Share Repurchase Programs (Details) - USD ($)		1 Months Ended	9 Months Ended	12 Months Ended
	Oct. 20, 2015	Jan. 31, 2015	Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2014	Oct. 31, 2014
Accelerated Share Repurchase Program [Member] | Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Authorized amount	$ 300,000,000
Stock repurchase program expiration date	15 months
Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Repurchased amount			$ 161,900,000	$ 175,000,000
Shares repurchased			5,673,686
Additional shares repurchased				6,177,455
Common Stock [Member] | Accelerated Share Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Authorized amount			$ 250,000,000	$ 250,000,000		$ 75,000,000.0
Repurchased amount				$ 250,000,000
Shares repurchased		391,612		9,100,000.0	2,510,460
Shares repurchased, average cost per share				$ 27.53