Share Repurchases - Additional Information (Details) - USD ($) shares in Millions, $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Nov. 02, 2016
Accelerated Share Repurchases [Line Items]
Stock repurchase program, authorized amount			$ 500.0
Stock purchases, shares	6.0
Payment for share repurchase	$ 300.0	$ 200.0
Evergreen Program
Accelerated Share Repurchases [Line Items]
Payment for share repurchase	125.0
Repurchase Program
Accelerated Share Repurchases [Line Items]
Payment for share repurchase	175.0
Remaining amount for share repurchase program	$ 125.0