Stockholders' Equity - Stock Repurchase Plan (Details) - USD ($)	2 Months Ended	12 Months Ended			39 Months Ended
	May 25, 2018	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2018	Oct. 31, 2017	Jan. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repurchased stock value		$ 149,687,000	$ 12,572,000	$ 94,200,000
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
Remaining authorized repurchase amount						$ 65,294,000
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
2015 And 2017 Stock Repurchase Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining authorized repurchase amount		$ 250,607,000			$ 250,607,000	$ 400,294,000
Shares repurchased (in shares)		1,702,653	222,471	1,420,349	3,722,502
Repurchased stock value		$ 149,687,000	$ 12,572,000	$ 94,200,000	$ 284,393,000
Repurchased stock acquired average cost per share (in dollars per share)		$ 87.91	$ 56.51	$ 66.32	$ 76.40
Subsequent Event | 2015 And 2017 Stock Repurchase Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining authorized repurchase amount	$ 250,607,000
Shares repurchased (in shares)	3,722,502
Repurchased stock value	$ 284,393,000
Repurchased stock acquired average cost per share (in dollars per share)	$ 76.40