Segment Reporting - Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Total plant, equipment and leasehold improvement additions									$ 14,879	$ 20,063	$ 15,568
Revenues	$ 67,380	$ 81,202	$ 73,725	$ 86,393	$ 93,567	$ 107,697	$ 95,536	$ 77,310	308,700	374,110	261,006
Total long-lived assets	171,763				179,224				171,763	179,224
Total North America
Segment Reporting Information [Line Items]
Total plant, equipment and leasehold improvement additions									13,432	19,404	15,114
Revenues									274,542	328,652	212,551
Total long-lived assets	160,672				166,631				160,672	166,631
U.S.
Segment Reporting Information [Line Items]
Total plant, equipment and leasehold improvement additions									13,169	19,129	15,082
Revenues									262,544	316,111	196,418
Total long-lived assets	157,773				164,377				157,773	164,377
Canada
Segment Reporting Information [Line Items]
Total plant, equipment and leasehold improvement additions									263	275	32
Revenues									11,998	12,541	16,133
Total long-lived assets	2,899				2,254				2,899	2,254
U.K.
Segment Reporting Information [Line Items]
Total plant, equipment and leasehold improvement additions									1,447	659	454
Revenues									25,705	36,954	36,682
Total long-lived assets	$ 11,091				$ 12,593				11,091	12,593
Other
Segment Reporting Information [Line Items]
Revenues									$ 8,453	$ 8,504	$ 11,773