Stockholders' Equity - Capital Stock and Share Repurchases (Details) - USD ($)	3 Months Ended						9 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Nov. 08, 2018	Apr. 03, 2017
Equity [Abstract]
Initial authorization										$ 2,000,000,000.0
Additional authorization									$ 2,000,000,000.0
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased (in shares)	2,353,852	6,220,190	7,359,609	12,452,514	1,448,729	3,779,194	15,933,651	17,680,437
Average price per share (in dollars per share)	$ 36.68	$ 40.18	$ 54.35	$ 63.96	$ 87.16	$ 85.86	$ 46.21	$ 70.58
Amount	$ 86,000,000	$ 250,000,000	$ 400,000,000	$ 797,000,000	$ 127,000,000	$ 324,000,000	$ 736,000,000	$ 1,248,000,000
Open market purchases
Equity, Class of Treasury Stock [Line Items]
Number of shares repurchased (in shares)	2,353,852	4,414,840	5,510,415	12,452,514	1,448,729	3,779,194
Average price per share (in dollars per share)	$ 36.68	$ 33.96	$ 54.44	$ 63.96	$ 87.16	$ 85.86
Amount	$ 86,000,000	$ 150,000,000	$ 300,000,000	$ 797,000,000	$ 127,000,000	$ 324,000,000
ASR
Equity, Class of Treasury Stock [Line Items]
Payments for repurchase of shares			200,000,000
Prepayments for share repurchases			$ 100,000,000
Number of shares repurchased (in shares)	0	1,805,350	1,849,194	0	0	0	3,654,544
Average price per share (in dollars per share)	$ 0	$ 55.39	$ 54.08	$ 0	$ 0	$ 0	$ 54.73
Amount	$ 0	$ 100,000,000	$ 100,000,000	$ 0	$ 0	$ 0	$ 200,000,000