Income Taxes Unrecognized Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Balance at beginning of year	$ 2,438	$ 2,373	$ 1,944
Current period tax positions	523	456	492
Lapse of statute of limitations	(411)	(391)	(63)
Balance at end of year	2,550	2,438	$ 2,373
Unrecognized tax benefits that would impact effective tax rate	540
Interest and penalties in income tax expense related to unrecognized tax positions	42	43
Income tax penalties and interest accrued	$ 616	$ 574