Segment and Related Information - Revenue by Geographic Region (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) segment	Sep. 30, 2021 USD ($)
Consulting Fee Revenue and Total Revenue by Geographic Region:
Number of reporting units | segment			1
Total revenue	$ 109,571	$ 96,604	$ 317,537	$ 285,237
Americas
Consulting Fee Revenue and Total Revenue by Geographic Region:
Total revenue	57,875	51,362	166,666	147,701
Middle East/Asia/Pacific
Consulting Fee Revenue and Total Revenue by Geographic Region:
Total revenue	25,378	21,621	75,892	63,320
Europe
Consulting Fee Revenue and Total Revenue by Geographic Region:
Total revenue	16,284	13,897	46,220	44,942
Africa
Consulting Fee Revenue and Total Revenue by Geographic Region:
Total revenue	$ 10,034	$ 9,724	$ 28,759	$ 29,274
Geographic Concentration Risk | Revenue Benchmark
Consulting Fee Revenue and Total Revenue by Geographic Region:
Percentage of total revenue	100.00%	100.00%	100.00%	100.00%
Geographic Concentration Risk | Revenue Benchmark | Americas
Consulting Fee Revenue and Total Revenue by Geographic Region:
Percentage of total revenue	52.70%	53.10%	52.40%	51.70%
Geographic Concentration Risk | Revenue Benchmark | Middle East/Asia/Pacific
Consulting Fee Revenue and Total Revenue by Geographic Region:
Percentage of total revenue	23.20%	22.40%	23.90%	22.20%
Geographic Concentration Risk | Revenue Benchmark | Europe
Consulting Fee Revenue and Total Revenue by Geographic Region:
Percentage of total revenue	14.90%	14.40%	14.60%	15.80%
Geographic Concentration Risk | Revenue Benchmark | Africa
Consulting Fee Revenue and Total Revenue by Geographic Region:
Percentage of total revenue	9.20%	10.10%	9.10%	10.30%
Consulting fee revenue
Consulting Fee Revenue and Total Revenue by Geographic Region:
Total revenue	$ 85,142	$ 77,061	$ 254,262	$ 227,158
Consulting fee revenue | Americas
Consulting Fee Revenue and Total Revenue by Geographic Region:
Total revenue	37,896	34,510	113,572	100,996
Consulting fee revenue | Middle East/Asia/Pacific
Consulting Fee Revenue and Total Revenue by Geographic Region:
Total revenue	23,436	21,345	72,305	62,100
Consulting fee revenue | Europe
Consulting Fee Revenue and Total Revenue by Geographic Region:
Total revenue	14,500	12,328	41,618	36,968
Consulting fee revenue | Africa
Consulting Fee Revenue and Total Revenue by Geographic Region:
Total revenue	$ 9,310	$ 8,878	$ 26,767	$ 27,094
Consulting fee revenue | Geographic Concentration Risk | Revenue Benchmark
Consulting Fee Revenue and Total Revenue by Geographic Region:
Percentage of total revenue	99.90%	100.00%	100.00%	100.00%
Consulting fee revenue | Geographic Concentration Risk | Revenue Benchmark | Americas
Consulting Fee Revenue and Total Revenue by Geographic Region:
Percentage of total revenue	44.50%	44.80%	44.70%	44.50%
Consulting fee revenue | Geographic Concentration Risk | Revenue Benchmark | Middle East/Asia/Pacific
Consulting Fee Revenue and Total Revenue by Geographic Region:
Percentage of total revenue	27.50%	27.70%	28.40%	27.30%
Consulting fee revenue | Geographic Concentration Risk | Revenue Benchmark | Europe
Consulting Fee Revenue and Total Revenue by Geographic Region:
Percentage of total revenue	17.00%	16.00%	16.40%	16.30%
Consulting fee revenue | Geographic Concentration Risk | Revenue Benchmark | Africa
Consulting Fee Revenue and Total Revenue by Geographic Region:
Percentage of total revenue	10.90%	11.50%	10.50%	11.90%