Interim Consolidated Financial Statements - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Jan. 01, 2020
Summary Of Significant Accounting Policy [Line Items]
Total revenues	$ 113,781,000	$ 106,345,000
Decrease in retained earnings	$ 131,937,000		$ 127,981,000
ASU No. 2016-13 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020
ASU No. 2019-12 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2021
Change in accounting principle, accounting standards update, immaterial effect	true
ASU No. 2017-04 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020
Change in accounting principle, accounting standards update, immaterial effect	true
ASU No. 2018-13 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020
Change in accounting principle, accounting standards update, immaterial effect	true
ASU No. 2018-15 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020
Change in accounting principle, accounting standards update, immaterial effect	true
Cumulative Effect, Period of Adoption, Adjustment [Member] | ASU No. 2016-13 [Member]
Summary Of Significant Accounting Policy [Line Items]
Decrease in retained earnings				$ (200,000)
Consulting [Member]
Summary Of Significant Accounting Policy [Line Items]
Total revenues	$ 38,550,000	31,988,000
Research [Member]
Summary Of Significant Accounting Policy [Line Items]
Total revenues	74,968,000	$ 74,267,000
Reclassification Adjustment [Member]
Summary Of Significant Accounting Policy [Line Items]
Total revenues	0
Reclassification Adjustment [Member] | Consulting [Member]
Summary Of Significant Accounting Policy [Line Items]
Total revenues	(1,400,000)
Reclassification Adjustment [Member] | Research [Member]
Summary Of Significant Accounting Policy [Line Items]
Total revenues	$ 1,400,000