Income Taxes (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Income Taxes        
Federal income tax at U.S. statutory rate 23.70% 24.20% 24.00% 24.80%
Income Tax Expense (Benefit) $ 8,058 $ 6,562 $ 17,343 $ 16,430
Valuation allowance, deferred tax assets 0 $ 0 0 $ 0
Unrecognized tax benefits 2,300   2,300  
Unrecognized tax benefits, net of federal benefit 1,800   1,800  
Accrual for interest and penalties $ 200   $ 200