Share Repurchase - Additional Information (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jan. 28, 2015
Accelerated Share Repurchases [Line Items]
Stock repurchase program, authorized amount				$ 500.0
Stock purchases, shares	4.4
Payment for share repurchase	$ 363.1	$ 478.8	$ 50.1
accelerated share repurchase contract
Accelerated Share Repurchases [Line Items]
Stock purchases, shares	2.6
Payment for share repurchase	$ 215.0
Evergreen Program
Accelerated Share Repurchases [Line Items]
Payment for share repurchase	88.0
Repurchase Program
Accelerated Share Repurchases [Line Items]
Payment for share repurchase	275.1
Remaining amount for share repurchase program	$ 224.9