Summary of Significant Accounting Policies - Summary of Revenue by Region (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation Of Revenue [Line Items]
Revenue	$ 55,204	$ 51,804	$ 114,443	$ 99,861
Service
Disaggregation Of Revenue [Line Items]
Revenue	$ 55,204	$ 51,804	$ 114,443	$ 99,861
Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | Service
Disaggregation Of Revenue [Line Items]
Percentage of Revenue	100.00%	100.00%	100.00%	100.00%
United States
Disaggregation Of Revenue [Line Items]
Revenue	$ 38,613	$ 36,068	$ 78,965	$ 68,428
United States | Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | Service
Disaggregation Of Revenue [Line Items]
Percentage of Revenue	70.00%	70.00%	69.00%	69.00%
United Kingdom
Disaggregation Of Revenue [Line Items]
Revenue	$ 12,335	$ 11,766	$ 26,240	$ 24,982
United Kingdom | Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | Service
Disaggregation Of Revenue [Line Items]
Percentage of Revenue	22.00%	23.00%	23.00%	25.00%
Canada
Disaggregation Of Revenue [Line Items]
Revenue	$ 2,748	$ 2,339	$ 5,988	$ 3,948
Canada | Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | Service
Disaggregation Of Revenue [Line Items]
Percentage of Revenue	5.00%	4.00%	5.00%	4.00%
Other
Disaggregation Of Revenue [Line Items]
Revenue	$ 1,508	$ 1,631	$ 3,250	$ 2,503
Other | Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | Service
Disaggregation Of Revenue [Line Items]
Percentage of Revenue	3.00%	3.00%	3.00%	2.00%
International
Disaggregation Of Revenue [Line Items]
Revenue	$ 16,591	$ 15,736	$ 35,478	$ 31,433
International | Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | Service
Disaggregation Of Revenue [Line Items]
Percentage of Revenue	30.00%	30.00%	31.00%	31.00%