Related Party Transactions (Detail) - Schedule of quarterly net asset value and net asset value per Unit since commencement of operations (USD $)	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Jan. 01, 2010
Price at Commencement (January 1, 2010)	1,000
Number Of Units (in Shares)	90,232.65				61,814.26				15,160.08
All Other Purposes [Member] \| WC Diversified Series [Member] \| B 0 Members [Member]
Price at Commencement (January 1, 2010)													1,000.000
Net Asset Value (in Dollars)	$ 59,085,151	$ 57,230,448	$ 54,723,265	$ 50,681,169	$ 39,815,854	$ 33,859,556	$ 21,259,372	$ 14,437,218	$ 7,609,887	$ 3,449,930	$ 1,552,311	$ 204,747
Net Asset Value per Unit	1,062.610	1,066.471	1,064.657	1,108.358	1,123.309	1,129.120	1,066.753	1,096.377	1,082.475	1,045.693	1,025.067	1,016.543
Total return after performance fee, from the commencement of operations through the year ended December 31, 2011	6.26%
All Other Purposes [Member] \| WC Diversified Series [Member] \| B 2 Members [Member]
Price at Commencement (January 1, 2010)													1,000.000
Net Asset Value (in Dollars)	34,902,966	35,467,117	31,902,551	30,271,135	28,671,748	25,506,034	18,552,025	11,718,602	8,686,430	4,167,206	3,545,196	711,568
Net Asset Value per Unit	1,007.915	1,016.800	1,020.267	1,067.511	1,087.324	1,098.429	1,042.152	1,076.859	1,068.441	1,037.254	1,020.653	1,012.822
Total return after performance fee, from the commencement of operations through the year ended December 31, 2011	0.79%
Financial Reporting [Member] \| WC Diversified Series [Member] \| B 0 Members [Member]
Price at Commencement (January 1, 2010)													1,000.000
Net Asset Value (in Dollars)	59,061,278	57,203,593	54,693,424	50,648,343	39,780,045	33,820,763	21,217,596	14,392,458	7,562,143	3,399,202	1,498,597	170,129
Net Asset Value per Unit	1,062.181	1,065.970	1,064.077	1,107.640	1,122.299	1,127.826	1,064.656	1,092.977	1,075.684	1,030.317	989.597	844.668
Total return after performance fee, from the commencement of operations through the year ended December 31, 2011	6.22%
Financial Reporting [Member] \| WC Diversified Series [Member] \| B 2 Members [Member]
Price at Commencement (January 1, 2010)													1,000.000
Net Asset Value (in Dollars)	$ 34,879,095	$ 35,440,260	$ 31,872,713	$ 30,238,312	$ 28,635,941	$ 25,467,241	$ 18,510,249	$ 11,673,842	$ 8,638,686	$ 4,116,477	$ 3,491,483	$ 676,948
Net Asset Value per Unit	1,007.226	1,016.030	1,019.313	1,066.354	1,085.966	1,096.758	1,039.805	1,072.746	1,062.568	1,024.627	1,005.189	963.546
Total return after performance fee, from the commencement of operations through the year ended December 31, 2011	0.72%
WC Diversified Series [Member] \| B 0 Members [Member]
Number Of Units (in Shares)	55,603.78	53,663.40	51,399.89	45,726.34	35,445.16	29,987.57	19,929.06	13,168.12	7,030.08	3,299.18	1,514.35	201.42
WC Diversified Series [Member] \| B 2 Members [Member]
Number Of Units (in Shares)	34,628.87	34,881.13	31,268.81	28,356.74	26,369.10	23,220.46	17,801.65	10,882.20	8,130.00	4,017.54	3,473.46	702.56

AlphaMetrix Managed Futures III LLC 10-K