Stockholders' Equity - Repurchase Programs (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended				6 Months Ended
	Oct. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2019
Equity, Class of Treasury Stock [Line Items]
Dollar value of shares remaining for repurchase		$ 159,807				$ 159,807
Shares repurchased (in shares)						1,296,201
Repurchased stock acquired average cost per share (in dollars per share)						$ 146.89
Dollar value of shares repurchased		$ 155,400	$ 35,005	$ 124,736	$ 9,999	$ 190,405
Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Dollar value of shares remaining for repurchase	$ 159,807
Shares repurchased (in shares)	0