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Summary of Significant Accounting Policies - Additional Information (Detail) |  |  | 12 Months Ended |
--- | --- | --- | --- | ---
Jan. 01, 2019 USD ($) | Jan. 02, 2018 USD ($) | Dec. 31, 2019 USD ($) ConsumerandBusinessLeader Customer shares | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Jan. 03, 2019 USD ($)
Summary Of Significant Accounting Policy [Line Items] |  |  |  |  |  |
Operating lease right-of-use assets |  |  | $ 69,100,000 |  |  |
Operating lease liabilities |  |  | $ 79,270,000 |  |  |
Lease package practical expedients |  |  | true |  |  |
Reclassification adjustment to retained earnings for tax effects |  |  |  | $ 3,803,000 | $ (419,000) |
Deferred revenue |  |  | $ 179,194,000 | 135,332,000 |  |
Prepaid expenses and other current assets |  |  | 19,201,000 | 12,802,000 |  |
Deferred commissions |  |  | 20,326,000 | 15,677,000 |  |
Other assets |  |  | 6,829,000 | 5,310,000 |  |
Retained earnings |  |  | $ 118,147,000 | 127,717,000 |  |
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 1% or 1% of total | Customer |  |  | 0 |  |  |
Annual goodwill impairment test, period |  |  | November 30th |  |  |
Goodwill impairment charges | $ 0 |  | $ 0 | 0 | 0 |
Non-current deferred rent liabilities |  |  |  | 6,602,000 |  |
Foreign exchange losses |  |  | (933,000) | (603,000) | (632,000) |
Contract assets |  |  | $ 0 |  |  |
Contract with customer, contract duration |  |  | 1 year |  |  |
Deferred revenue recognized |  |  | $ 147,200,000 | 134,700,000 |  |
Revenue expected to be recognized |  |  | 372,000,000 |  |  |
Amortization expense related to deferred commissions |  |  | $ 36,000,000 | 32,200,000 |  |
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. |  |  |
Advertising expense |  |  | $ 1,300,000 | 600,000 | $ 700,000 |
Stock options granted | shares |  |  | 0 |  |  |
Unamortized fair value stock based compensation |  |  |  | $ 21,200,000 |  |
Weighted average remaining recognition period |  |  | 2 years 3 months 18 days |  |  |
Research Service Revenue [Member] | Customer Concentration Risk [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policy [Line Items] |  |  |  |  |  |
Customer accounted for percentage |  |  | 4.00% |  |  |
Accounts Receivable [Member] | Credit Concentration Risk [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policy [Line Items] |  |  |  |  |  |
Customer accounted for percentage |  |  | 4.00% |  |  |
Topic 842 [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policy [Line Items] |  |  |  |  |  |
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 |  |  |  |  |
Topic 842 [Member] | SiriusDecisions, Inc [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policy [Line Items] |  |  |  |  |  |
Operating lease right-of-use assets |  |  |  |  |  | $ 10,400,000
Operating lease liabilities |  |  |  |  |  | $ 10,400,000
ASU No. 2018-02 [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policy [Line Items] |  |  |  |  |  |
Reclassification adjustment to retained earnings for tax effects |  | $ 26,000 |  |  |  |
Topic 606 [Member] | Initial Application Period Cumulative Effect Transition [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policy [Line Items] |  |  |  |  |  |
Deferred revenue |  |  | $ 7,800,000 |  |  |
Prepaid expenses and other current assets |  |  | (5,500,000) |  |  |
Deferred commissions |  |  | 900,000 |  |  |
Other assets |  |  | 600,000 |  |  |
Retained earnings |  |  | $ 3,800,000 |  |  |
Minimum [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policy [Line Items] |  |  |  |  |  |
Number of consumers and business leaders included in annual surveys | ConsumerandBusinessLeader |  |  | 690,000 |  |  |
Advisory services period |  |  | 1 hour |  |  |
Consulting services period |  |  | 14 days |  |  |
Maximum [Member] |  |  |  |  |  |
Summary Of Significant Accounting Policy [Line Items] |  |  |  |  |  |
Advisory services period |  |  | 2 days |  |  |
Consulting services period |  |  | 3 months |  |  |
Contract with customer, expected payment term |  |  | one year |  |  |

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