Stockholders' Equity - Narrative (Details) - USD ($) shares in Millions	3 Months Ended	6 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Apr. 24, 2018
Class of Stock [Line Items]
Number of shares repurchased (shares)	1.1	2.6
Cost of shares repurchased	$ 38,100,000	$ 87,500,000
Amount available for future purchase	$ 419,300,000	$ 419,300,000
April 2018 Stock Repurchase Program
Class of Stock [Line Items]
Stock repurchase program, additional authorized repurchase amount			$ 400,000,000