Income Taxes Company's uncertain tax positions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Balance as of the beginning of the year	$ 9,216	$ 9,066
Tax positions related to current year:
Additions	165	152
Reductions	(9)	(14)
Tax positions related to prior years:
Additions	26	80
Reductions	(6)	(4)
Settlements	0	0
Lapses in statute of limitations	(48)	(64)
Balance as of the end of the year	9,344	9,216
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	332
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	56
Unrecognized tax benfits, reduction in accrued interest and penalties	$ 6	$ 12