Revenue Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Services	$ 393,662	$ 375,830	$ 379,743	$ 326,968	$ 402,747	$ 375,800	$ 390,532	$ 344,700	$ 1,476,203	$ 1,513,779	$ 1,385,785
United States
Disaggregation of Revenue [Line Items]
Services									1,153,192	1,172,364	1,103,714
Canada
Disaggregation of Revenue [Line Items]
Services									124,000	123,092	124,101
Other Geographical Location [Member]
Disaggregation of Revenue [Line Items]
Services									199,011	218,323	157,970
Food & Beverage [Member]
Disaggregation of Revenue [Line Items]
Services									313,368	313,786	266,600
Retail [Member]
Disaggregation of Revenue [Line Items]
Services									152,552	178,152	182,428
Consumer Products [Member]
Disaggregation of Revenue [Line Items]
Services									162,524	162,307	147,849
Communications [Member]
Disaggregation of Revenue [Line Items]
Services									178,410	208,701	160,064
Automotive [Member]
Disaggregation of Revenue [Line Items]
Services									88,807	127,023	129,352
Technology [Member]
Disaggregation of Revenue [Line Items]
Services									104,479	99,325	109,309
Health Care [Member]
Disaggregation of Revenue [Line Items]
Services									127,547	124,261	115,159
Financials [Member]
Disaggregation of Revenue [Line Items]
Services									110,069	104,713	85,480
Transportation and Travel/Lodging [Member]
Disaggregation of Revenue [Line Items]
Services									86,419	56,955	58,298
Other [Member]
Disaggregation of Revenue [Line Items]
Services									152,028	$ 138,556	$ 131,246
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Services									51,636
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member] | United States
Disaggregation of Revenue [Line Items]
Services									20,699
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member] | Canada
Disaggregation of Revenue [Line Items]
Services									(1,288)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member] | Other Geographical Location [Member]
Disaggregation of Revenue [Line Items]
Services									32,225
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member] | Food & Beverage [Member]
Disaggregation of Revenue [Line Items]
Services									7,064
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member] | Retail [Member]
Disaggregation of Revenue [Line Items]
Services									(2,683)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member] | Consumer Products [Member]
Disaggregation of Revenue [Line Items]
Services									585
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member] | Communications [Member]
Disaggregation of Revenue [Line Items]
Services									25,957
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member] | Automotive [Member]
Disaggregation of Revenue [Line Items]
Services									8,587
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member] | Technology [Member]
Disaggregation of Revenue [Line Items]
Services									38
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member] | Health Care [Member]
Disaggregation of Revenue [Line Items]
Services									507
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member] | Financials [Member]
Disaggregation of Revenue [Line Items]
Services									146
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member] | Transportation and Travel/Lodging [Member]
Disaggregation of Revenue [Line Items]
Services									2,461
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Services									8,974
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Disaggregation of Revenue [Line Items]
Services									1,527,839
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | United States
Disaggregation of Revenue [Line Items]
Services									1,173,891
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Canada
Disaggregation of Revenue [Line Items]
Services									122,712
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Other Geographical Location [Member]
Disaggregation of Revenue [Line Items]
Services									231,236
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Food & Beverage [Member]
Disaggregation of Revenue [Line Items]
Services									320,432
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Retail [Member]
Disaggregation of Revenue [Line Items]
Services									149,869
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Consumer Products [Member]
Disaggregation of Revenue [Line Items]
Services									163,109
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Communications [Member]
Disaggregation of Revenue [Line Items]
Services									204,367
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Automotive [Member]
Disaggregation of Revenue [Line Items]
Services									97,394
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Technology [Member]
Disaggregation of Revenue [Line Items]
Services									104,517
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Health Care [Member]
Disaggregation of Revenue [Line Items]
Services									128,054
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Financials [Member]
Disaggregation of Revenue [Line Items]
Services									110,215
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Transportation and Travel/Lodging [Member]
Disaggregation of Revenue [Line Items]
Services									88,880
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Services									$ 161,002