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BASIS OF PREPARATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES. (Property and equipment) (Details)
12 Months Ended
Dec. 31, 2019
Computer and communications software and equipment  
Property, Plant and Equipment [Line Items]  
Estimated useful life 3 years
Buildings and improvements  
Property, Plant and Equipment [Line Items]  
Estimated useful life 32 years
Leasehold improvements  
Property, Plant and Equipment [Line Items]  
Estimated useful life 8 years
Furniture and other equipment  
Property, Plant and Equipment [Line Items]  
Estimated useful life 6 years
Leased land  
Property, Plant and Equipment [Line Items]  
Estimated useful life 99 years