Deferred Acquistion Costs Components of deferred acquisition (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred Acquisition Costs [Line Items]
Balance at January 1, net	$ 6,904	$ 6,325	$ 5,827
Additions	3,825	3,484
Amortization	3,246	2,986
Balance at December 31, net	$ 6,904	$ 6,325