Condensed Statements of Shareholders' Equity (USD $)
In Millions, unless otherwise specified
Total
Common Stock [Member]
Additional Paid-In Capital [Member]
Accumulated Other Comprehensive Loss [Member]
Retained Earnings [Member]
Balance at Dec. 31, 2010 $ 830.3 $ 79.6 $ 842.3 $ (261.8) $ 170.2
Balance (in shares) at Dec. 31, 2010   79.6      
Net income 223.0 0 0 0 223.0
Other comprehensive income (loss) (8.8) 0 0 (8.8) 0
Dividends paid:          
Common stock ($0.60 per share) (48.0) 0 0 0 (48.0)
Common stock repurchased and retired (2.2) (0.1) (2.1) 0 0
Common stock repurchased and retired (in shares) (0.1) (0.1)      
Common stock issued for:          
Stock options exercised 9.3 0.5 8.8 0 0
Stock options exercised (in shares) 0.5 0.5      
Other transactions 3.8 0.2 3.6 0 0
Other transactions (in shares)   0.2      
Stock-based compensation (0.2) 0 (0.2) 0 0
Balance at Sep. 30, 2011 1,007.2 80.2 852.4 (270.6) 345.2
Balance (in shares) at Sep. 30, 2011   80.2      
Balance at Dec. 31, 2011 985.8 80.1 852.0 (294.2) 347.9
Balance (in shares) at Dec. 31, 2011   80.1      
Net income 115.0 0 0 0 115.0
Other comprehensive income (loss) 21.6 0 0 21.6 0
Dividends paid:          
Common stock ($0.60 per share) (48.0) 0 0 0 (48.0)
Common stock repurchased and retired (3.1) (0.2) (2.9) 0 0
Common stock repurchased and retired (in shares) (0.2) (0.2)      
Common stock issued for:          
Stock options exercised 1.4 0.1 1.3 0 0
Stock options exercised (in shares) 0.1 0.1      
Other transactions 2.6 0.2 2.4 0 0
Other transactions (in shares)   0.2      
Stock-based compensation 1.3 0 1.3 0 0
Balance at Sep. 30, 2012 $ 1,076.6 $ 80.2 $ 854.1 $ (272.6) $ 414.9
Balance (in shares) at Sep. 30, 2012   80.2