Fair Value - Additional Information (Details)	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jan. 01, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, measurements other than fair value	$ 73,649,000	$ 96,840,000
Fair value, assets, level 2 to level 1 transfers, amount	3,200,000	0
Fair value, assets, level 2 to level 3 transfers, amount	0	0
Contingent payment arrangements	17,384,000	0		$ 0
Changes in estimates	(3,051,000)	(2,429,000)
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangements	22,911,000	7,336,000
Private equity investment venture capital fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investment			$ 1,000,000.0
Contingent payment arrangements | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent payment arrangements	22,900,000	7,300,000
Software publishing company
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, measurements other than fair value	1,000,000.0
Start-up company
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, measurements other than fair value	900,000	900,000
Equity method investee
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, measurements other than fair value	2,900,000	3,400,000
Broker dealer exchange memberships
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, measurements other than fair value	$ 3,200,000	$ 3,100,000
Revenue growth rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability, measurement input	0.50
Revenue growth rate | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability, measurement input	0.007
Revenue growth rate | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability, measurement input	0.025
Discount rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability, measurement input		0.030
Discount rate | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability, measurement input	0.104
Discount rate | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability, measurement input	0.035
Market price of risk adjustment rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability, measurement input	0.069
2016 Acquisition
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Changes in estimates	$ 3,100,000	$ 2,400,000