Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax [Line Items]
Corporate income tax rate		35.00%
Income tax (benefit) expense		$ (9,335,000)	$ 34,295,000	$ 23,852,000
Tax liability related to one-time tax on unremitted foreign earnings		363,000
Valuation reserve, Recorded		4,803,000	1,610,000
Excess tax benefits related to stock-based compensation			24,906,000	$ 27,830,000
Cumulative effect adjustment to retained earnings		$ 2,552,000
Income tax examination description		The Company is currently under examination in New York for corporate income tax returns for the tax years ended December 31, 2014, 2015 and 2016. The Company cannot predict with certainty whether there will be any additional tax liabilities, penalties and/or interest as a result of the audit. In June of 2017, the New York City Department of Finance completed a routine examination of Seamless Holdings Corporation for General Corporation Tax for the short tax period from October 17, 2012 through August 8, 2013 and proposed no changes. The Company does not expect any additional tax liabilities, penalties and/or interest as a result of the audit.
Unrecognized tax benefits that would impact effective tax rate		$ 1,300,000	1,000,000
Significant adjustments to unrecognized tax benefits within the next twelve months		As of December 31, 2017, the Company anticipates that a portion of the unrecognized tax benefit will be reversed in 2018 due to the closing of the statute of limitations for one of its tax positions.
Unrecognized tax benefits, estimated impact due to closing of statute of limitations		$ 800,000
Unrecognized Tax liabilities, penalties			0
Maximum
Income Tax [Line Items]
Unrecognized Tax liabilities, interest expense		100,000
ASU 2016-09
Income Tax [Line Items]
Cumulative effect adjustment to retained earnings		2,552,000
Illinois Edge | ASU 2016-09
Income Tax [Line Items]
Deferred tax assets, tax credit carryforwards		$ 700,000
U K Subsidiary
Income Tax [Line Items]
Tax exemption percentage on foreign source portion of dividends from foreign subsidiaries		100.00%
Withholding taxes on undistributed foreign earnings repatriated		$ 0
Additional tax liability, unremitted foreign earnings		0
Tax Cuts and Jobs Act
Income Tax [Line Items]
Income tax (benefit) expense		(34,100,000)
Tax liability related to one-time tax on unremitted foreign earnings		363,000
Tax Cuts and Jobs Act | U K Subsidiary
Income Tax [Line Items]
Tax liability related to one-time tax on unremitted foreign earnings		363,000
State Tax
Income Tax [Line Items]
Operating loss carryforwards		4,362,000	5,265,000
State Tax | ASU 2016-09
Income Tax [Line Items]
Excess tax benefits related to stock-based compensation		4,100,000
U.S. federal
Income Tax [Line Items]
Operating loss carryforwards		595,000	$ 483,000
U.S. federal | ASU 2016-09
Income Tax [Line Items]
Operating loss carryforwards		$ 100,000
Scenario Forecast
Income Tax [Line Items]
Corporate income tax rate	21.00%