Stockholders' Equity - Repurchase Programs (Details) - USD ($)	2 Months Ended	12 Months Ended
	May 17, 2019	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017	Jan. 31, 2019	Oct. 31, 2017
Class of Stock [Line Items]
Dollar value of shares that may yet be repurchased		$ 350,212,000
Repurchased stock acquired average cost per share (in dollars per share)		$ 115.22	$ 87.91	$ 56.51
Shares repurchased (in shares)		1,400,699	1,702,653	222,471
Dollar value of shares repurchased		$ 161,395,000	$ 149,687,000	$ 12,572,000
2015 And 2017 Stock Repurchase Plans
Class of Stock [Line Items]
Authorized amount of shares to repurchase						$ 400,294,000
2017 Stock Repurchase Program
Class of Stock [Line Items]
Dollar value of shares that may yet be repurchased		$ 89,212,000
2019 Stock Repurchase Plan
Class of Stock [Line Items]
Authorized amount of shares to repurchase					$ 261,000,000
Subsequent Event
Class of Stock [Line Items]
Shares repurchased (in shares)	0