Significant Accounting Policies - Furniture, Equipment, Purchased Software, Leasehold Improvements and Software Development Cost (Details)	9 Months Ended
	Sep. 30, 2020
Furniture, Equipment, Purchased Software and Leasehold Improvements | Minimum
Furniture, Equipment, Purchased Software and Leasehold Improvements
Useful life	3 years
Furniture, Equipment, Purchased Software and Leasehold Improvements | Maximum
Furniture, Equipment, Purchased Software and Leasehold Improvements
Useful life	7 years
Software Development Costs
Furniture, Equipment, Purchased Software and Leasehold Improvements
Useful life	3 years
Amortization of pushdown accounting allocation	9 years