Stock Repurchases (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Feb. 13, 2017
Equity, Class of Treasury Stock [Line Items]
Increase in number of shares authorized for repurchase					3,000,000
Number of shares authorized for repurchase		2,502,610
Common stock repurchased, shares		1,282,166	712,448	342,928
Common stock repurchased, value		$ 480.8	$ 300.4	$ 129.1
Open Market [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased, shares	[1]	1,267,103	669,752	336,743
Common stock repurchased, value	[1]	$ 474.3	$ 282.2	$ 127.1
Other [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchased, shares	[2]	15,063	42,696	6,185
Common stock repurchased, value	[2]	$ 6.5	$ 18.2	$ 2.0

[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 March 5, 2020, the board of directors authorized the repurchase of up to three million shares of our common stock in addition to the board’s prior authorizations. As of December 31, 2020, we had authorization to repurchase 2,502,610 shares of our common stock.

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