Stock Repurchases (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014		Mar. 07, 2013
Equity, Class of Treasury Stock [Line Items]
Increase in number of shares authorized for repurchase								1,000,000
Number of shares authorized for repurchase		364,788
Common stock repurchased, shares		666,330		470,071		2,686,744
Common stock repurchased, value		$ 121.7		$ 86.5		$ 343.7
Open Market [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased, shares		495,662	[1]	464,006	[1]	0
Common stock repurchased, value		$ 88.5	[1]	$ 85.4	[1]	$ 0.0
Tender Offer [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased, shares		0		0		2,548,868	[2]
Common stock repurchased, value		$ 0.0		$ 0.0		$ 325.3	[2]
Tender offer, offering costs		$ 0.3
Other [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased, shares	[3]	170,668		6,065		137,876
Common stock repurchased, value	[3]	$ 33.2		$ 1.1		$ 18.4

[1] Represents repurchases under authorizations by the board of directors for the repurchase of shares by us from time to time in the open market or in privately negotiated transactions. On November 23, 2015, the board of directors authorized the repurchase of up to one million shares of our common stock in addition to the board’s prior authorizations. As of December 31, 2016, we had authorization to repurchase 364,788 shares of our common stock.

[2] Tender offer cost amounts include transaction costs of $0.3 million for 2014.

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