Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating leases
Amount paid for capital leases	$ 57	$ 1,259	$ 177
Operating leases
Operating leases
Rent expense	13,100	12,400	$ 13,600
Future minimum payments due
2017	8,753
2018	8,500
2019	6,495
2020	3,889
2021	2,016
Thereafter	1,823
Total	31,476
Capital lease obligations | Equipment
Capital lease obligations
Current portion of capital leases	506	559
Long-term portion of capital leases	486	1,018
Total capital lease obligation	992	$ 1,577
Future minimum payments due
2018	506
2019	453
2020	32
2021	1
2022	0
Thereafter	0
Total	$ 992