Summary of Significant Accounting Policies - Additional Information (Detail)		12 Months Ended
	Jan. 02, 2018 USD ($)	Dec. 31, 2020 USD ($) ConsumerandBusinessLeader Customer shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Jan. 01, 2020 USD ($)	Jan. 01, 2019 USD ($)
Summary Of Significant Accounting Policy [Line Items]
Number of real time feedback votes included in annual surveys | Customer		45
Right-of-use asset impairments		$ 2,300,000
Leasehold impairments		1,100,000
(Decrease) increase in retained earnings		127,981,000	$ 118,147,000
Operating lease right-of-use assets		69,296,000	69,100,000
Operating lease liabilities		$ 82,295,000
Lease package practical expedients		true
Reclassification adjustment to retained earnings for tax effects				$ (26,000)
Deferred revenue		$ 179,968,000	179,194,000
Prepaid expenses and other current assets		18,588,000	19,201,000
Deferred commissions		23,620,000	20,326,000
Other assets		$ 5,524,000	6,829,000
Original maturities		90 days
Realized losses on sales of available-for-sale securities				200,000
Number of customers accounted for revenues or accounts receivable greater than 3% or 3% of total | Customer		0
Annual goodwill impairment test, period		November 30th
Goodwill impairment charges		$ 0	0	0
Long-lived asset impairment charges		3,400,000	0	0
Foreign exchange losses		(582,000)	(933,000)	(603,000)
Revenues from contracts with customers		448,984,000	461,697,000	357,575,000
Contract assets		$ 0
Contract with customer, contract duration		1 year
Deferred revenue recognized		$ 153,200,000	147,200,000
Revenue expected to be recognized		369,800,000
Amortization expense related to deferred commissions		40,000,000.0	36,000,000.0	32,200,000
Impairment of deferred commissions		$ 0	0	0
Option to extend description		Some of the Company’s leases include options to extend or terminate the lease. When determining the lease term, these options are included in the measurement and recognition of the Company’s ROU assets and lease liabilities when it is reasonably certain that the Company will exercise the option(s).
Advertising expense		$ 700,000	$ 1,300,000	$ 600,000
Stock options granted | shares		0	0	0
Unamortized fair value stock based compensation		$ 20,100,000
Weighted average remaining recognition period		2 years 9 months 18 days
Research Service Revenue [Member] | Customer Concentration Risk [Member]
Summary Of Significant Accounting Policy [Line Items]
Customer accounted for percentage		3.00%
Accounts Receivable [Member] | Credit Concentration Risk [Member]
Summary Of Significant Accounting Policy [Line Items]
Customer accounted for percentage		3.00%
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. 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
Topic 842 [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, 2019
Change in accounting principle, accounting standards update, immaterial effect		true
Operating lease right-of-use assets						$ 53,300,000
Operating lease liabilities						60,800,000
Topic 842 [Member] | Effect of Adoption [Member]
Summary Of Significant Accounting Policy [Line Items]
Deferred rent						$ 7,500,000
ASU No. 2016-15 [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, 2018
Change in accounting principle, accounting standards update, immaterial effect		true
ASU No. 2016-18 [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, 2018
Change in accounting principle, accounting standards update, immaterial effect		true
ASU No. 2017-01 [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, 2018
Change in accounting principle, accounting standards update, immaterial effect		true
ASU No. 2018-02 [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, 2018
ASU No. 2018-02 [Member] | Revision of Prior Period Accounting Standards Update Adjustment [Member]
Summary Of Significant Accounting Policy [Line Items]
Reclassification adjustment to retained earnings for tax effects	$ 26,000
ASU No. 2014-09 [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, 2018
ASU No. 2014-09 [Member] | Initial Application Period Cumulative Effect Transition [Member]
Summary Of Significant Accounting Policy [Line Items]
(Decrease) increase in retained earnings		$ 3,800,000
Deferred revenue		7,800,000
Prepaid expenses and other current assets		(5,500,000)
Deferred commissions		900,000
Other assets		$ 600,000
Cumulative Effect, Period of Adoption, Adjustment [Member] | ASU No. 2016-13 [Member]
Summary Of Significant Accounting Policy [Line Items]
(Decrease) increase in retained earnings					$ (200,000)
Minimum [Member]
Summary Of Significant Accounting Policy [Line Items]
Number of consumers and business leaders and technology leaders included in annual surveys | ConsumerandBusinessLeader		675,000
Consulting services period		14 days
Advisory services period		1 hour
Maximum [Member]
Summary Of Significant Accounting Policy [Line Items]
Consulting services period		3 months
Advisory services period		2 days
Contract with customer, expected payment term		one year