Quarterly report pursuant to Section 13 or 15(d)

Income Taxes (Details)

v3.8.0.1
Income Taxes (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2017
Dec. 31, 2016
Income Tax Disclosure [Abstract]            
Income tax expense $ 108,901 $ 111,556 $ 342,387 $ 326,108    
Income Taxes [Line Items]            
Effective income tax rate percent 28.30% 36.50% 33.30% 37.60%    
Valuation allowance $ 44,828   $ 44,828     $ 47,682
Forecast            
Income Taxes [Line Items]            
Effective income tax rate percent         34.00%