Income Taxes - Expense (benefit) reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes
Statutory federal income tax rate (as a percent)	21.00%	35.00%	35.00%
Tax at the statutory federal rate	$ 6,643	$ 14,594	$ 8,065
State income taxes (net of federal benefit)	1,392	1,340	806
Decrease in valuation allowance, net	(4,993)	(142)	(941)
Decrease in uncertain tax positions	(2,165)
Change in US tax law	(1,035)	(33,542)
Dividend received deduction	(322)	(530)	(40)
Other permanent items	(256)	399	(743)
Total income tax (benefit) expense	$ (736)	$ (17,881)	$ 7,147