Income Taxes and Related Payments - Components of provision for income taxes (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Current:
Federal	$ 4,589	$ 5,234	$ 8,738	$ 7,858
State and local	828	640	1,595	1,001
Foreign	115	120	232	227
Total	5,532	5,994	10,565	9,086
Deferred:
Federal	5,769	8,463	12,249	17,598
State and local	686	484	1,458	1,006
Total	6,455	8,947	13,707	18,604
Income tax expense	$ 11,987	$ 14,941	$ 24,272	$ 27,690

Amount of current federal tax expense (benefit) pertaining to income (loss) from continuing operations.

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