Consolidated Statements Of Changes In Shareholders' Equity (USD $) In Millions, except Share data, unless otherwise specified	Total	Common Stock	Accumulated Other Comprehensive Income	Retained Earnings
Balance at Dec. 31, 2010	$ 1,894.6	$ 158.2	$ 160.9	$ 1,575.5
Balance, shares at Dec. 31, 2010		46,159,387
Changes in Shareholders' Equity
Net income	136.7			136.7
Other comprehensive income, net of tax	74.2		74.2
Common stock:
Repurchased	(90.3)	(90.3)
Shares repurchased		(2,180,100)
Issued under share-based compensation plans, net	14.5	14.5
Issued under share-based compensation plans net, shares		289,572
Dividends declared on common stock	(39.3)			(39.3)
Balance at Dec. 31, 2011	1,990.4	82.4	235.1	1,672.9
Balance, shares at Dec. 31, 2011		44,268,859
Changes in Shareholders' Equity
Net income	100.1			100.1
Other comprehensive income, net of tax	78.9		78.9
Common stock:
Repurchased	(10.0)	(10.0)
Shares repurchased		(279,700)
Issued under share-based compensation plans, net	11.7	11.7
Issued under share-based compensation plans net, shares		250,449
Balance at Sep. 30, 2012	$ 2,171.1	$ 84.1	$ 314.0	$ 1,773.0
Balance, shares at Sep. 30, 2012		44,239,608