Consolidated Statement of Shareholders' Equity (Unaudited) - 6 months ended Jun. 30, 2017 - USD ($) shares in Millions, $ in Millions	Total		Preferred Stock	Common Stock	Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Balance as of December 31, 2016 at Dec. 31, 2016	$ 1,045.5		$ 0.0	$ 1.6	$ 2,857.3	$ (1,673.8)	$ (139.6)
Preferred stock, issued, beginning balance (in shares) at Dec. 31, 2016	0.0		0.0
Common stock, shares issued, beginning balance (in shares) at Dec. 31, 2016	160.3			160.3
Shareholders' Equity (Deficit) [Roll Forward]
Net income	$ 198.7					198.7
Equity-based compensation expense	20.7				20.7
Stock option exercises	7.4				7.4
Stock option exercises (in shares)				1.3
Coworker Stock Purchase Plan	4.7				4.7
Coworker Stock Purchase Plan (in shares)				0.1
Repurchases of common stock	(359.4)			$ (0.1)		(359.3)
Repurchases of common stock (in shares)				(6.1)
Dividends	(50.3)				0.4	(50.7)
Incentive compensation plan shares withheld for taxes	(42.0)					(42.0)
Foreign currency translation	25.4	[1]					25.4
Unrealized loss from hedge accounting	(1.6)						(1.6)
Balance as of June 30, 2017 at Jun. 30, 2017	$ 849.1		$ 0.0	$ 1.5	$ 2,890.5	$ (1,927.1)	$ (115.8)
Preferred stock, issued, ending balance (in shares) at Jun. 30, 2017	0.0		0.0
Common stock, shares issued, ending balance (in shares) at Jun. 30, 2017	155.6			155.6

[1] (1) Net of tax (expense) benefit of $0.1 million and $0.3 million for three months ended June 30, 2017 and 2016, and net of tax (expense) benefit of $0.1 million and $0.3 million for six months ended June 30, 2017 and 2016, respectively.