Segment Reporting - Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Total plant, equipment and leasehold improvement additions									$ 20,063	$ 15,568	$ 10,628
Revenues	$ 93,567	$ 107,697	$ 95,536	$ 77,310	$ 87,865	$ 77,374	$ 53,236	$ 42,531	374,110	261,006	196,370
Total long-lived assets	179,224				177,276				179,224	177,276
Total North America
Segment Reporting Information [Line Items]
Total plant, equipment and leasehold improvement additions									19,404	15,114	9,804
Revenues									328,652	212,551	153,186
Total long-lived assets	166,631				162,669				166,631	162,669
U.S.
Segment Reporting Information [Line Items]
Total plant, equipment and leasehold improvement additions									19,129	15,082	9,679
Revenues									316,111	196,418	135,525
Total long-lived assets	164,377				160,144				164,377	160,144
Canada
Segment Reporting Information [Line Items]
Total plant, equipment and leasehold improvement additions									275	32	125
Revenues									12,541	16,133	17,661
Total long-lived assets	2,254				2,525				2,254	2,525
U.K.
Segment Reporting Information [Line Items]
Total plant, equipment and leasehold improvement additions									659	454	824
Revenues									36,954	36,682	32,448
Total long-lived assets	$ 12,593				$ 14,607				12,593	14,607
Other
Segment Reporting Information [Line Items]
Revenues									$ 8,504	$ 11,773	$ 10,736