Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions		Common Stock	Additional Paid-In Capital	Deferred Compensation Equity	Accumulated Other Comprehensive Income (loss).	Retained Earnings	Shares in Treasury	Total
Balance at Dec. 31, 2012		$ 78.7	$ 171.4	$ 0.6	$ (35.5)	$ 1,788.3	$ (215.4)	$ 1,788.1
Balance (in shares) at Dec. 31, 2012		63,127,299					15,249,714
Increase (Decrease) in Shareholders' Equity
Net income						209.7		209.7
Other comprehensive income (loss), net of tax					4.0			4.0
Cash dividends - $0.84, $0.94, and $1.10 per share for the years ended 2013, 2014, and 2015, respectively						(53.7)		(53.7)
Stock based compensation (1)	[1]		29.7	2.4			$ 5.9	38.0
Stock based compensation other (in shares)	[1]	531,478					(488,233)
Balance at Dec. 31, 2013		$ 78.7	201.1	3.0	(31.5)	1,944.3	$ (209.5)	1,986.1
Balance (in shares) at Dec. 31, 2013		63,658,777					14,761,481
Increase (Decrease) in Shareholders' Equity
Net income						251.3		251.3
Other comprehensive income (loss), net of tax					(30.3)			(30.3)
Cash dividends - $0.84, $0.94, and $1.10 per share for the years ended 2013, 2014, and 2015, respectively						(61.2)		(61.2)
Stock based compensation (1)	[1]		46.7	3.0			$ 9.4	59.1
Stock based compensation other (in shares)	[1]	1,032,282					(1,038,280)
Balance at Dec. 31, 2014		$ 78.7	247.8	6.0	(61.8)	2,134.4	$ (200.1)	$ 2,205.0
Balance (in shares) at Dec. 31, 2014		64,691,059					13,723,201	64,691,059
Increase (Decrease) in Shareholders' Equity
Net income						319.7		$ 319.7
Other comprehensive income (loss), net of tax					(25.3)			(25.3)
Cash dividends - $0.84, $0.94, and $1.10 per share for the years ended 2013, 2014, and 2015, respectively						(72.3)		(72.3)
Common stock repurchase	[1]						$ (137.2)	(137.2)
Common stock repurchase (in Shares)	[1]	(1,496,411)					1,496,411
Stock based compensation (1)			45.6	2.0			$ 9.9	57.5
Stock based compensation other (in shares)		856,952					(836,371)
Balance at Dec. 31, 2015		$ 78.7	$ 293.4	$ 8.0	$ (87.1)	$ 2,381.8	$ (327.4)	$ 2,347.4
Balance (in shares) at Dec. 31, 2015		64,051,600					14,383,241	64,051,600

[1] Stock based compensation includes stock option activity, net of tax, and restricted share activity