Stockholders' Equity - Stock Repurchase Plan (Details) - USD ($)	6 Months Ended	33 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Nov. 09, 2017	Jan. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares repurchased (in shares)	0
2015 Stock Repurchase Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum stock repurchase amount approved by Board of Directors				$ 200,000,000
Shares purchased since inception (in shares)		2,020,000,000
Repurchased stock value		$ 135,000,000
Repurchased stock acquired average cost per share		$ 66.69
Remaining authorized repurchase amount	$ 65,000,000	$ 65,000,000
Subsequent Event | 2017 Stock Repurchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum stock repurchase amount approved by Board of Directors			$ 335,000,000
Subsequent Event | 2015 And 2017 Stock Repurchase Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining authorized repurchase amount			$ 400,000,000