Impact of Adopting Topic 606 5 (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating activities:
Net income	$ 129	$ 184	$ 295	$ 362
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			163	190
Deferred income taxes			(12)	(23)
Provision for bad debts			0	2
Share-based compensation expense			68	61
Other non-cash items			5	2
Foreign currency transaction (gains) losses			(4)	9
Changes in other operating assets and liabilities, net of effect of acquisitions:
Decrease in trade accounts receivable			279	317
Increase in contract assets			(26)	0
Decrease in contract costs			18	0
Decrease in deferred revenue and advanced payments			(314)	(460)
Decrease in taxes payable, net			(258)	(58)
Increase in accounts payable, accrued expenses and other			33	11
Decrease in accrued salaries, wages and commissions			(34)	(81)
Changes in other operating assets and liabilities, net			38	3
Net cash provided by operating activities			251	$ 335
As Reported under Topic 606
Operating activities:
Net income	129		295
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			163
Deferred income taxes			(12)
Provision for bad debts			0
Share-based compensation expense			68
Other non-cash items			5
Foreign currency transaction (gains) losses			(4)
Changes in other operating assets and liabilities, net of effect of acquisitions:
Decrease in trade accounts receivable			279
Increase in contract assets			(26)
Decrease in contract costs			18
Decrease in deferred revenue and advanced payments			(314)
Decrease in taxes payable, net			(258)
Increase in accounts payable, accrued expenses and other			33
Decrease in accrued salaries, wages and commissions			(34)
Changes in other operating assets and liabilities, net			38
Net cash provided by operating activities			251
Proforma as if the previous accounting of Topic 605 was in effect
Operating activities:
Net income	245		506
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			163
Deferred income taxes			(10)
Provision for bad debts			(1)
Share-based compensation expense			68
Other non-cash items			5
Foreign currency transaction (gains) losses			2
Changes in other operating assets and liabilities, net of effect of acquisitions:
Decrease in trade accounts receivable			275
Increase in contract assets			0
Decrease in contract costs			0
Decrease in deferred revenue and advanced payments			(598)
Decrease in taxes payable, net			(204)
Increase in accounts payable, accrued expenses and other			35
Decrease in accrued salaries, wages and commissions			(34)
Changes in other operating assets and liabilities, net			44
Net cash provided by operating activities			251
Effect of Change Higher/(Lower)
Operating activities:
Net income	$ (116)		(211)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			0
Deferred income taxes			(2)
Provision for bad debts			1
Share-based compensation expense			0
Other non-cash items			0
Foreign currency transaction (gains) losses			(6)
Changes in other operating assets and liabilities, net of effect of acquisitions:
Decrease in trade accounts receivable			4
Increase in contract assets			(26)
Decrease in contract costs			18
Decrease in deferred revenue and advanced payments			284
Decrease in taxes payable, net			(54)
Increase in accounts payable, accrued expenses and other			(2)
Decrease in accrued salaries, wages and commissions			0
Changes in other operating assets and liabilities, net			(6)
Net cash provided by operating activities			$ 0

CA, INC. 10-Q