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ACCOUNTING POLICIES ACCOUNTING POLICIES - Summary of Equity Investment Ownerships (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 370,881,000	$ 347,099,000	$ 373,709,000	$ 367,729,000	$ 452,548,000	$ 440,580,000	$ 483,133,000	$ 445,331,000	$ 1,459,418,000	$ 1,821,592,000	$ 1,744,756,000
Equity Method Investment, Summarized Financial Information, Net Income (Loss)									7,734,000	3,869,000	508,000
Equity Method Investment, Other than Temporary Impairment									1,382,000	0	0
Equity Method Investment, Realized Gain (Loss) on Disposal									$ 524,000	0	0
Bitt Inc.
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	21.00%								21.00%
Spera, Inc.
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	19.00%								19.00%
Voatz, Inc.
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	20.00%								20.00%
SettleMint NV [Member] [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	29.00%								29.00%
Chainstone Labs
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	29.00%								29.00%
Finclusive [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	10.00%								10.00%
Minds, Inc.
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	24.00%								24.00%
PeerNova, Inc. [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	11.00%								11.00%
VinX Network Ltd.
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	29.00%								29.00%
GrainChain, Inc.
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	18.00%								18.00%
Boston Security Token Exchange LLC
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	50.00%								50.00%
Medici Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax									$ 2,749,000	$ 2,362,000	$ 159,000