Consolidated Statements Of Shareholders' Equity - USD ($) $ in Millions	Total	Share Capital	Treasury Shares		Accumulated Other Comprehensive Loss	Retained Earnings
Balance, at beginning of period at Dec. 31, 2013		$ 419.0	$ (80.0)		$ 0.0	$ 3,180.8
Net income	$ 490.3					490.3
Dividends						(81.7)
Stock compensation			19.6	[1]		5.6
Share repurchases	(175.4)		(175.4)
Shares cancelled		(11.0)	92.7			(81.7)
Foreign currency translation adjustment	0.0				0.0
Balance, at end of period at Dec. 31, 2014	3,778.2	408.0	(143.1)		0.0	3,513.3
Net income	83.9					83.9
Dividends						(92.4)
Stock compensation			19.6	[1]		(2.2)
Share repurchases	(245.3)		(245.3)
Shares cancelled		(21.3)	213.7			(192.4)
Foreign currency translation adjustment	(9.3)				(9.3)
Balance, at end of period at Dec. 31, 2015	3,532.5	386.7	(155.1)		(9.3)	3,310.2
Net income	255.3					255.3
Dividends						(91.5)
Stock compensation			20.9	[1]		3.2
Share repurchases	(166.3)		(166.3)
Shares cancelled		(7.9)	66.7			(58.8)
Foreign currency translation adjustment	(2.3)				(2.3)
Balance, at end of period at Dec. 31, 2016	$ 3,551.8	$ 378.8	$ (233.8)		$ (11.6)	$ 3,418.4

[1] Includes stock compensation expense for the period and shares issued out of treasury for awards exercised or vested. See note 2(o) to the notes to the consolidated financial statements.