Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ / shares in Units, shares in Millions							1 Months Ended		3 Months Ended				12 Months Ended
	Feb. 19, 2020	Dec. 26, 2019	Oct. 29, 2019	Oct. 28, 2019	Jun. 01, 2019	Sep. 04, 2018	Oct. 31, 2018	Sep. 30, 2018	Dec. 31, 2019	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Dec. 31, 2020	Dec. 31, 2019	Nov. 19, 2020
Business Acquisition [Line Items]
Amortization expense relating to intangible assets													$ 20,500,000	$ 66,800,000
Equity Method Investment, Ownership Percentage															27.00%
Impairment loss													20,400,000	5,700,000
Amortization expense relating to purchased intangible assets													5,200,000	$ 2,100,000
DBOT
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage								99.00%				99.00%
Finite-lived Intangible Assets Acquired										$ 8,300,000
Impairment loss													9,300,000
SolidOpinion, Inc ("SolidOpinion")
Business Acquisition [Line Items]
Total purchase price paid											$ 7,200,000
Cash paid to acquire entity											$ 2,500,000
Number of shares exchange	0.5										4.5
Fintalk
Business Acquisition [Line Items]
Total purchase price paid							$ 6,400,000	$ 7,000,000.0
Cash paid to acquire entity							1,000,000.0	1,000,000.0
Number of shares exchange					2.9
Value of capital stock issued							$ 5,400,000	$ 6,000,000.0
Impairment loss									$ 5,700,000
Grapevine Logic, Inc. ("Grapevine")
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage								65.70%				65.70%
Cash paid to acquire entity						$ 2,400,000
Tree Technologies
Business Acquisition [Line Items]
Equity Method Investment, Ownership Percentage									51.00%					51.00%
Cash paid to acquire entity		$ 900,000
Value of capital stock issued													$ 11,300,000
Influencer network
Business Acquisition [Line Items]
Impairment loss												$ 800,000
Customer Lists [Member]
Business Acquisition [Line Items]
Value of capital stock issued										600,000
Impairment loss										7,100,000
Weighted Average Remaining Useful Life (in years)													0 years
Customer Lists [Member] | DBOT
Business Acquisition [Line Items]
Impairment loss										$ 30,000
Marketing and Distribution Agreement [Member]
Business Acquisition [Line Items]
Impairment loss													$ 12,500,000
Weighted Average Remaining Useful Life (in years)													0 years
GTB Tokens
Business Acquisition [Line Items]
Number of shares exchange											8.3
Impairment loss									$ 61,100,000					$ 61,100,000
Quote price of GTB			$ 1.84	$ 17.00					$ 0.23