Investments (Securities Held to Maturity) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 7,121,439	$ 6,841,543
Gross Unrealized Gains	302,044	357,805
Gross Unrealized Losses	(52,887)	(23,905)
Fair Value	7,370,596	7,175,443
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	1,710,436	183,821
Less than 12 Months, Unrealized Losses	(35,475)	(3,307)
12 Months or Greater, Fair Value	416,430	951,284
12 Months or Greater, Unrealized Losses	(17,412)	(20,598)
Total, Fair Value	2,126,866	1,135,105
Total, Unrealized Losses	(52,887)	(23,905)
U.S. Agencies [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	15,038	10,061
Gross Unrealized Gains	517	705
Gross Unrealized Losses	(137)	0
Fair Value	15,418	10,766
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	4,858
Less than 12 Months, Unrealized Losses	(137)
12 Months or Greater, Fair Value	0
12 Months or Greater, Unrealized Losses	0
Total, Fair Value	4,858
Total, Unrealized Losses	(137)	0
U.S. Treasury [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,923	1,920
Gross Unrealized Gains	369	409
Gross Unrealized Losses	0	0
Fair Value	2,292	2,329
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Total, Unrealized Losses	0	0
States and Political Subdivisions [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	439,504	432,186
Gross Unrealized Gains	26,535	31,417
Gross Unrealized Losses	(2,536)	(336)
Fair Value	463,503	463,267
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	65,904	0
Less than 12 Months, Unrealized Losses	(1,633)	0
12 Months or Greater, Fair Value	12,567	23,076
12 Months or Greater, Unrealized Losses	(903)	(336)
Total, Fair Value	78,471	23,076
Total, Unrealized Losses	(2,536)	(336)
Foreign Governments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	0
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Fair Value	0
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Total, Unrealized Losses	0
Public Utilities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,010,342	978,847
Gross Unrealized Gains	53,640	67,836
Gross Unrealized Losses	(4,433)	(757)
Fair Value	1,059,549	1,045,926
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	228,627	7,078
Less than 12 Months, Unrealized Losses	(3,727)	(13)
12 Months or Greater, Fair Value	17,802	48,198
12 Months or Greater, Unrealized Losses	(706)	(744)
Total, Fair Value	246,429	55,276
Total, Unrealized Losses	(4,433)	(757)
Corporate [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	4,056,712	3,754,222
Gross Unrealized Gains	153,167	183,650
Gross Unrealized Losses	(37,448)	(18,591)
Fair Value	4,172,431	3,919,281
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	1,176,531	156,839
Less than 12 Months, Unrealized Losses	(25,477)	(2,997)
12 Months or Greater, Fair Value	300,133	698,316
12 Months or Greater, Unrealized Losses	(11,971)	(15,594)
Total, Fair Value	1,476,664	855,155
Total, Unrealized Losses	(37,448)	(18,591)
Mortgage-backed [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,575,798	1,640,582
Gross Unrealized Gains	62,921	68,726
Gross Unrealized Losses	(8,333)	(4,164)
Fair Value	1,630,386	1,705,144
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	234,516	17,698
Less than 12 Months, Unrealized Losses	(4,501)	(240)
12 Months or Greater, Fair Value	85,928	181,694
12 Months or Greater, Unrealized Losses	(3,832)	(3,924)
Total, Fair Value	320,444	199,392
Total, Unrealized Losses	(8,333)	(4,164)
Home Equity [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	18,380	18,886
Gross Unrealized Gains	4,574	4,734
Gross Unrealized Losses	0	(57)
Fair Value	22,954	23,563
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value		2,206
Less than 12 Months, Unrealized Losses		(57)
12 Months or Greater, Fair Value		0
12 Months or Greater, Unrealized Losses		0
Total, Fair Value		2,206
Total, Unrealized Losses	0	(57)
Manufactured Housing [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	3,742	4,839
Gross Unrealized Gains	321	328
Gross Unrealized Losses	0	0
Fair Value	4,063	5,167
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Total, Unrealized Losses	$ 0	$ 0

NATIONAL WESTERN LIFE INSURANCE CO 10-Q