Acquisitions 2 (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2016	Jul. 08, 2015
Business Combinations [Abstract]
Accrued acquisition-related costs related to purchase price amounts withheld to support indemnification obligations	$ 12			$ 12		$ 3
Business Acquisition
Total revenue	1,007		$ 1,034	3,024	$ 3,016
Net income (loss)	$ 208		$ 223	$ 618	609
Rally
Business Acquisition
Percentage of outstanding shares of common stock acquired							100.00%
Purchase price		$ 519					$ 519
Fiscal Year 2016 Acquisitions | General and Administrative
Business Acquisition
Transaction costs			less than $1 million
Transaction costs					$ 20
Rally and Xceedium
Business Acquisition
Total revenue		35
Net income (loss)		$ (5)