Condensed Consolidated Statement of Equity - 9 months ended Sep. 30, 2017 - USD ($) $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Non Controlling Interests
Balance at Dec. 31, 2016	$ 696.8	$ 0.0	$ (667.9)	$ 584.0	$ 861.9	$ (81.5)	$ 0.3
Balance (in shares) at Dec. 31, 2016	42,932,994	42,932,994
Increase (Decrease) in Stockholders' Equity
Net income	$ 98.0				98.0		0.0
Other comprehensive income (loss):
Unrealized gain on available-for-sale investments, net of income tax of $1.1	3.5					3.5	0.0
Reclassification of adjustments for gain included in net income, net of income tax of $0.3	(0.8)					(0.8)	0.0
Foreign currency translation adjustment	29.9					29.9	0.0
Other comprehensive income, net	32.6					32.6	0.0
Issuance of common stock related to stock-option exercises and vesting of restricted stock units, net of shares withheld for taxes on settlements of restricted stock units	(3.2)	$ 0.0	1.0	(4.2)
Issuance of common stock related to stock-option exercises and vesting of restricted stock units, net of shares withheld for taxes on settlements of restricted stock units (in shares)		130,086
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition
Stock-based compensation	16.5			16.5
Common share repurchased	(40.6)		(40.6)
Common share repurchased (in shares)		(533,371)
Dividends declared	(19.7)				(19.7)
Purchase of additional interest in majority-owned investment	(1.2)	$ 0.0	0.0	(0.9)	0.0	0.0	(0.3)
Balance at Sep. 30, 2017	$ 779.2	$ 0.0	$ (707.5)	$ 595.4	$ 940.2	$ (48.9)	$ 0.0
Balance (in shares) at Sep. 30, 2017	42,529,709	42,529,709