Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Federal:
Current									$ 972	$ 1,062	$ 642
Deferred									37	24	387
Federal income tax provision (benefit)									1,009	1,086	1,029
State and local:
Current									333	402	237
Deferred									(1,011)	(1,670)	(754)
State and local income tax provision (benefit)									(678)	(1,268)	(517)
Changes in valuation allowance									790	1,606	493
Provision (benefit) for income taxes	$ 498	$ 188	$ 166	$ 268	$ 2,081	$ (1,643)	$ 641	$ 345	$ 1,121	$ 1,424	$ 1,005