Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Services	$ 362,130	$ 379,743	$ 690,921	$ 706,711
United States
Disaggregation of Revenue [Line Items]
Services	284,659	295,268	547,676	551,792
Canada
Disaggregation of Revenue [Line Items]
Services	24,564	33,086	46,942	59,465
Other
Disaggregation of Revenue [Line Items]
Services	52,907	51,389	96,303	95,454
Food & Beverage
Disaggregation of Revenue [Line Items]
Services	73,305	84,464	139,969	147,932
Retail
Disaggregation of Revenue [Line Items]
Services	39,894	38,396	72,350	76,411
Consumer Products
Disaggregation of Revenue [Line Items]
Services	45,296	41,367	78,232	77,973
Communications
Disaggregation of Revenue [Line Items]
Services	47,793	43,097	87,490	81,454
Automotive
Disaggregation of Revenue [Line Items]
Services	18,541	25,294	36,732	45,788
Technology
Disaggregation of Revenue [Line Items]
Services	28,876	23,540	54,279	45,080
Healthcare
Disaggregation of Revenue [Line Items]
Services	25,954	35,426	49,161	68,002
Financials
Disaggregation of Revenue [Line Items]
Services	27,868	30,207	52,795	52,702
Transportation and Travel/Lodging
Disaggregation of Revenue [Line Items]
Services	27,050	18,776	44,085	33,664
Other
Disaggregation of Revenue [Line Items]
Services	$ 27,553	$ 39,176	$ 75,828	$ 77,705