Employee Benefit Plans - Status of Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plans
Change in benefit obligation:
Beginning of year		$ 0	$ 2,016
Service cost			0
Interest cost			36
Actuarial loss (gain)			(9)
Benefits paid			(2,043)
Benefit obligation at end of year			0
Post-employment benefits
Change in benefit obligation:
Beginning of year	$ 4,106	4,681	4,926
Service cost	25	36	51
Interest cost	122	142	141
Actuarial loss (gain)	(261)	(297)	45
Benefits paid	(388)	(456)	(482)
Benefit obligation at end of year	$ 3,604	$ 4,106	$ 4,681