Consolidated Statement 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 the beginning of the period 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
Increase (Decrease) in Shareholders' Equity
Net income								134.3
Other comprehensive income (loss), net of tax					(7.1)			(7.1)
Cash dividends - $0.94 and $0.60 for the year ended 2015 and the six months ended June 30, 2016, respectively								(33.1)
Balance at the end of the period at Jun. 30, 2015					(68.9)
Balance at the beginning of the period 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
Increase (Decrease) in Shareholders' Equity
Net income						319.7		319.7
Other comprehensive income (loss), net of tax					(25.3)			(25.3)
Cash dividends - $0.94 and $0.60 for the year ended 2015 and the six months ended June 30, 2016, respectively						(72.3)		(72.3)
Repurchases of Common Stock							$ (137.2)	(137.2)
Repurchases of Common Stock (in Shares)		(1,496,411)					1,496,411
Issuances for stock based compensation (1)	[1]		45.6	2.0			$ 9.9	57.5
Issuances for stock based compensation (in shares)	[1]	856,952					(836,371)
Balance at the end of the period 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
Balance at the beginning of the period at Mar. 31, 2015					(81.8)
Increase (Decrease) in Shareholders' Equity
Net income								$ 94.9
Other comprehensive income (loss), net of tax					12.9			12.9
Cash dividends - $0.94 and $0.60 for the year ended 2015 and the six months ended June 30, 2016, respectively								(16.4)
Balance at the end of the period at Jun. 30, 2015					(68.9)
Balance at the beginning of the period at Dec. 31, 2015		$ 78.7	293.4	8.0	(87.1)	2,381.8	$ (327.4)	2,347.4
Increase (Decrease) in Shareholders' Equity
Net income						183.7		183.7
Other comprehensive income (loss), net of tax					(4.3)			(4.3)
Cash dividends - $0.94 and $0.60 for the year ended 2015 and the six months ended June 30, 2016, respectively						(39.0)		(39.0)
Repurchases of Common Stock							$ (41.5)	(41.5)
Repurchases of Common Stock (in Shares)		(459,662)					459,662
Issuances for stock based compensation (1)	[1]		25.5	2.4			$ 15.9	43.8
Issuances for stock based compensation (in shares)	[1]	808,705					(809,293)
Balance at the end of the period at Jun. 30, 2016		$ 78.7	318.9	10.4	(91.4)	2,526.5	$ (353.0)	$ 2,490.1
Balance (in shares) at Jun. 30, 2016		64,400,643					14,033,610	64,400,643
Balance at the beginning of the period at Mar. 31, 2016					(76.7)
Increase (Decrease) in Shareholders' Equity
Net income								$ 115.2
Other comprehensive income (loss), net of tax					(14.7)			(14.7)
Cash dividends - $0.94 and $0.60 for the year ended 2015 and the six months ended June 30, 2016, respectively								(19.5)
Balance at the end of the period at Jun. 30, 2016		$ 78.7	$ 318.9	$ 10.4	$ (91.4)	$ 2,526.5	$ (353.0)	$ 2,490.1
Balance (in shares) at Jun. 30, 2016		64,400,643					14,033,610	64,400,643

[1] Issuances for stock based compensation includes shares issued from treasury to cover stock option exercises, restricted and performance share releases, net of shares repurchased to cover employee taxes