Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Services	$ 381,975	$ 342,907	$ 362,130	$ 328,791	$ 393,662	$ 375,830	$ 379,743	$ 326,968	$ 1,415,803	$ 1,476,203	$ 1,513,779
United States
Disaggregation of Revenue [Line Items]
Services									1,116,045	1,153,191	1,172,364
Canada
Disaggregation of Revenue [Line Items]
Services									105,067	124,001	123,093
Other
Disaggregation of Revenue [Line Items]
Services									194,691	199,011	218,322
Food & Beverage
Disaggregation of Revenue [Line Items]
Services									280,094	313,368	313,786
Retail
Disaggregation of Revenue [Line Items]
Services									148,851	152,552	178,152
Consumer Products
Disaggregation of Revenue [Line Items]
Services									167,324	162,524	162,307
Communications
Disaggregation of Revenue [Line Items]
Services									184,870	178,410	208,701
Automotive
Disaggregation of Revenue [Line Items]
Services									78,985	88,807	127,023
Technology
Disaggregation of Revenue [Line Items]
Services									118,169	104,479	99,325
Healthcare
Disaggregation of Revenue [Line Items]
Services									102,221	127,547	124,261
Financials
Disaggregation of Revenue [Line Items]
Services									112,351	110,069	104,713
Transportation and Travel/Lodging
Disaggregation of Revenue [Line Items]
Services									88,958	86,419	56,955
Other
Disaggregation of Revenue [Line Items]
Services									$ 133,980	$ 152,028	$ 138,556