Income Taxes (Components of Income Tax) (Details) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Income Taxes [Line Items]      
Income from U.S. operations before income taxes $ 319,800,000 $ 158,700,000 $ 137,300,000
Current tax expense 147,739,000 107,241,000 52,402,000
Deferred tax expense (44,336,000) (37,925,000) (5,894,000)
Total income tax expense (benefit) 103,403,000 69,316,000 46,508,000
United States
     
Income Taxes [Line Items]      
Current tax expense 146,484,000 94,834,000 52,297,000
Deferred tax expense (44,180,000) (38,441,000) (6,066,000)
Canada
     
Income Taxes [Line Items]      
Income from Canadian operations before income taxes 82,300,000 31,600,000 1,000,000
Current tax expense 1,255,000 12,407,000 105,000
Deferred tax expense $ (156,000) $ 516,000 $ 172,000