Segment and Geographical Information - Additional Information (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2017 operating_segment	Dec. 31, 2015 Segment
Segment Reporting [Abstract]
Number of operating segments	8
Number of operating segments, operations management	6
Number of operating segments, finance and accounting	1
Number of operating segments, company provides operations management services	6
Number of non-operations management services	2
Number of reportable segments in prior periods | Segment		2