UNAUDITED CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (USD $) In Millions, except Share data in Thousands	Common stock [Member]	Additional capital in excess of par value [Member]	Retained earnings [Member]	Accumulated other comprehensive income [Member]	Total
Balances at Dec. 31, 2010	$ 51.7	$ 506.3	$ 2,599.4	$ 139.1	$ 3,296.5
Balances (shares) at Dec. 31, 2010					258,760
Comprehensive income
Net income			399.3		399.3
Net unrealized holding gains, net of tax				17.5	17.5
Currency translation adjustment, net of tax				0.3	0.3
Total comprehensive income					417.1
Dividends			(160.7)		(160.7)
Common stock-based compensation plans activity
Shares issued upon option exercises	0.3	35.6			35.9
Shares issued upon option exercises (shares)	1,668
Restricted shares issued, net of shares withheld for taxes	0.1	(0.1)			0
Restricted shares issued, net of shares withheld for taxes (shares)	128
Shares issued upon vesting of restricted stock units	0	0			0
Shares issued upon vesting of restricted stock units (shares)	3
Forfeiture of restricted awards	0	0			0
Forfeiture of restricted awards (shares)	(14)
Net tax benefits		18.7			18.7
Stock-based compensation expense		46.4			46.4
Common shares repurchased	(0.8)	(146.5)	(93.8)		(241.1)
Common shares repurchased (shares)	(4,027)
Balances at Jun. 30, 2011	$ 51.3	$ 460.4	$ 2,744.2	$ 156.9	$ 3,412.8
Balances (shares) at Jun. 30, 2011					256,518