Consolidated Statements Of Stockholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Common stock	Additional paid-in capital	Retained earnings (Accumulated deficit)	Accumulated other comprehensive income (loss)	Repurchase program, total
Balance at Mar. 31, 2013	$ 2,267	$ 3	$ 2,174	$ 21	$ 69
Balance (in shares) at Mar. 31, 2013		302,164
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	(24)			8	(32)
Issuance of common stock	16		16
Issuance of common stock (in shares)		9,278
Stock-based compensation	150		150
Tax benefit from stock-based compensation	13		13
Balance at Mar. 31, 2014	2,422	$ 3	2,353	29	37
Balance (in shares) at Mar. 31, 2014		311,442
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	840			875	(35)
Issuance of common stock	(24)		(24)
Issuance of common stock (in shares)		6,508
Reclassification of equity component of convertible notes	(31)		(31)
Repurchase and retirement of common stock	(337)		(337)			$ (337)
Stock repurchased and retired during period, Shares		(8,269)				8,200
Stock-based compensation	144		144
Tax benefit from stock-based compensation	22		22
Balance at Mar. 31, 2015	$ 3,036	$ 3	2,127	904	2
Balance (in shares) at Mar. 31, 2015	310,000	309,681
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	$ 1,138			1,156	(18)
Issuance of common stock	(49)		(49)
Issuance of common stock (in shares)		6,645
Reclassification of equity component of convertible notes	29		29
Settlement of convertible notes	$ (1)		(1)
Settlement of Convertible Notes	7,823	7,823
Exercise of convertible note hedge	(7,823)	(7,823)
Repurchase and retirement of common stock	$ (1,018)		(1,018)			$ (1,018)
Stock repurchased and retired during period, Shares		(15,724)				15,700
Stock-based compensation	178		178
Tax benefit from stock-based compensation	83		83
Balance at Mar. 31, 2016	$ 3,396	$ 3	$ 1,349	$ 2,060	$ (16)
Balance (in shares) at Mar. 31, 2016	301,000	300,602