Income Taxes (Details) (USD $)
In Millions, except Per Share data, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Income Taxes    
Income tax provision $ 9.9 $ 11.3
Effective income tax rate (as a percent) 15.30% 18.30%
Decrease in foreign income taxes due to special income tax concession in Singapore $ 2.3 $ 1.9
Impact of income tax concession on basic earnings per common share (in dollars per share) $ 0.03 $ 0.03
Impact of income tax concession on diluted earnings per common share (in dollars per share) $ 0.03 $ 0.03