Summary of Significant Accounting Policies - Additional Information (Detail)		12 Months Ended
	Nov. 30, 2021 USD ($)	Dec. 31, 2021 USD ($) d Customer ReportingUnit Segment $ / shares	Dec. 31, 2020 USD ($) Customer	Dec. 31, 2019 USD ($)	Feb. 11, 2022 USD ($)	Jun. 30, 2020 $ / shares	May 31, 2017 USD ($) $ / shares
Schedule Of Accounting Policies [Line Items]
Number of operating segment | Segment		1
Average stock price | $ / shares		$ 592.48
Cash and cash equivalents, maturity description		three months or less at the date of purchase, consisting primarily of money-market funds.
Restricted cash related to letters of credit for leased facilities		$ 3,000,000.0	$ 3,000,000.0
Impairment charges of long lived assets		$ 0
Number of reporting unit | ReportingUnit		1
Goodwill impairment	$ 0	$ 0	0	$ 0
Advertising expense		$ 37,300,000	21,900,000	14,900,000
Revenue subscription contract period		one year or less
Off-balance sheet risk amount		$ 0
Accounts receivable payment period		30 days
Maximum percentage of refundable credit of eligible research and development expenses incurred		25.00%
Amortization of software development costs, exclusive of costs recorded within property and equipment		$ 23,000,000.0	$ 16,000,000.0	$ 11,600,000
Minimum percentage chances of tax benefit to be realized on examination		50.00%
Accounts Receivable [Member] | Customer Concentration Risk [Member]
Schedule Of Accounting Policies [Line Items]
Number of customers represented more than 10% | Customer		0	0
Revenue [Member] | Customer Concentration Risk [Member]
Schedule Of Accounting Policies [Line Items]
Number of customers represented more than 10% | Customer		0	0
Internal Use Software [Member]
Schedule Of Accounting Policies [Line Items]
Property and equipment, estimated useful life		5 years
Maximum [Member]
Schedule Of Accounting Policies [Line Items]
Business combination, measurement period		1 year
Maximum [Member] | Capitalized Software Development Costs [Member]
Schedule Of Accounting Policies [Line Items]
Property and equipment, estimated useful life		5 years
Minimum [Member] | Capitalized Software Development Costs [Member]
Schedule Of Accounting Policies [Line Items]
Property and equipment, estimated useful life		2 years
0.25% Convertible Senior Notes Due 2022 as Liability Component [Member]
Schedule Of Accounting Policies [Line Items]
Common stock conversion price | $ / shares		$ 94.77
Debt instrument, convertible, threshold trading days | d		20
Debt instrument, convertible, threshold consecutive trading days | d		30
Percentage of closing price to trigger debt conversion		130.00%
Principal amount of long term debt		$ 19,382,000	$ 125,839,000
0.25% Convertible Senior Notes Due 2022 as Liability Component [Member] | Subsequent Event [Member]
Schedule Of Accounting Policies [Line Items]
Principal amount of long term debt					$ 0
0.375% Convertible Senior Notes Due 2025 [Member]
Schedule Of Accounting Policies [Line Items]
Common stock conversion price | $ / shares		$ 282.52				$ 282.52
Debt instrument, convertible, threshold trading days | d		20
Debt instrument, convertible, threshold consecutive trading days | d		30
Principal amount of long term debt		$ 900,000
0.375% Convertible Senior Notes Due 2025 [Member] | Maximum [Member]
Schedule Of Accounting Policies [Line Items]
Percentage of closing price to trigger debt conversion		130.00%
0.375% Convertible Senior Notes Due 2025 [Member] | Subsequent Event [Member]
Schedule Of Accounting Policies [Line Items]
Principal amount of long term debt					0
0.25% Convertible Senior Notes Due 2022 [Member]
Schedule Of Accounting Policies [Line Items]
Common stock conversion price | $ / shares							$ 94.77
Debt instrument, convertible, threshold trading days | d		20
Debt instrument, convertible, threshold consecutive trading days | d		30
Principal amount of long term debt		$ 106,500,000					$ 1,000,000,000
0.25% Convertible Senior Notes Due 2022 [Member] | Maximum [Member]
Schedule Of Accounting Policies [Line Items]
Common stock conversion price | $ / shares		$ 115.83
Percentage of closing price to trigger debt conversion		130.00%
0.25% Convertible Senior Notes Due 2022 [Member] | Minimum [Member]
Schedule Of Accounting Policies [Line Items]
Common stock conversion price | $ / shares		$ 94.77
0.25% Convertible Senior Notes Due 2022 [Member] | Subsequent Event [Member]
Schedule Of Accounting Policies [Line Items]
Principal amount of long term debt					$ 0