Stock Repurchases (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Mar. 07, 2013
Equity, Class of Treasury Stock [Line Items]
Increase in number of shares authorized for repurchase					1,000,000
Remaining number of shares authorized for repurchase	324,456
Common stock repurchased, shares	6,065		775,296
Common stock repurchased, value	$ 1.1		$ 103.6
Tender Offer [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased, shares	0		637,420
Common stock repurchased, value	0		85.2	[1]
Tender offer, offering costs			0.2
Other [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased, shares	6,065	[2]	137,876	[2]
Common stock repurchased, value	$ 1.1	[2]	$ 18.4	[2]

[1] Tender Offer Cost amount includes offering costs of $0.2 million for the three months ended March 31, 2014.

[2] Represents shares of common stock released to us as payment of tax withholdings due to us upon the vesting of restricted stock and restricted stock units.