Interim Consolidated Financial Statements - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Jan. 01, 2020
Summary Of Significant Accounting Policy [Line Items]
Total revenues	$ 128,670,000	$ 113,541,000	$ 242,451,000	$ 219,886,000
Decrease in retained earnings	$ 140,280,000		$ 140,280,000		$ 127,981,000
ASU No. 2016-13 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in accounting principle, accounting standards update, adopted	true		true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020		Jan. 01, 2020
ASU No. 2019-12 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in accounting principle, accounting standards update, adopted	true		true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2021		Jan. 01, 2021
Change in accounting principle, accounting standards update, immaterial effect	true		true
ASU No. 2017-04 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in accounting principle, accounting standards update, adopted	true		true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020		Jan. 01, 2020
Change in accounting principle, accounting standards update, immaterial effect	true		true
ASU No. 2018-13 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in accounting principle, accounting standards update, adopted	true		true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020		Jan. 01, 2020
Change in accounting principle, accounting standards update, immaterial effect	true		true
ASU No. 2018-15 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in accounting principle, accounting standards update, adopted	true		true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020		Jan. 01, 2020
Change in accounting principle, accounting standards update, immaterial effect	true		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	$ 40,960,000	33,475,000	$ 79,510,000	65,463,000
Research [Member]
Summary Of Significant Accounting Policy [Line Items]
Total revenues	81,002,000	$ 75,034,000	155,970,000	$ 149,301,000
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)		(2,900,000)
Reclassification Adjustment [Member] | Research [Member]
Summary Of Significant Accounting Policy [Line Items]
Total revenues	$ 1,400,000		$ 2,900,000