Income Taxes - Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Federal tax expense (benefit):
Current									$ 8,543	$ 8,540	$ 10,113
Deferred									376	(742)	14,290
Federal tax expense (benefit)									8,919	7,798	24,403
State and local tax expense (benefit):
Current									4,067	1,985	1,672
Deferred									(199)	(151)	903
State and local tax expense (benefit)									3,868	1,834	2,575
Income tax expense	$ 3,052	$ 4,845	$ 2,280	$ 2,610	$ 2,314	$ 3,081	$ 1,893	$ 2,344	$ 12,787	$ 9,632	$ 26,978