Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Services	$ 342,907	$ 375,830	$ 1,033,828	$ 1,082,541
United States
Disaggregation of Revenue [Line Items]
Services	271,671	296,544	819,347	848,336
Canada
Disaggregation of Revenue [Line Items]
Services	25,895	32,132	72,837	91,597
Other
Disaggregation of Revenue [Line Items]
Services	45,341	47,154	141,644	142,608
Food & Beverage
Disaggregation of Revenue [Line Items]
Services	64,774	80,919	204,743	234,203
Retail
Disaggregation of Revenue [Line Items]
Services	39,420	40,421	111,899	116,832
Consumer Products
Disaggregation of Revenue [Line Items]
Services	38,510	40,124	119,866	118,097
Communications
Disaggregation of Revenue [Line Items]
Services	48,147	46,779	136,819	128,232
Automotive
Disaggregation of Revenue [Line Items]
Services	19,125	21,282	55,857	67,070
Technology
Disaggregation of Revenue [Line Items]
Services	28,148	26,005	84,294	71,085
Healthcare
Disaggregation of Revenue [Line Items]
Services	25,152	33,751	74,403	101,753
Financials
Disaggregation of Revenue [Line Items]
Services	28,054	30,378	81,049	83,079
Transportation and Travel/Lodging
Disaggregation of Revenue [Line Items]
Services	20,541	19,357	65,111	53,021
Other
Disaggregation of Revenue [Line Items]
Services	$ 31,036	$ 36,814	$ 99,787	$ 109,169