Income Taxes - Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of income tax rate:
U.S. Federal statutory tax rate	21.00%	21.00%	35.00%
Permanent items	(3.00%)	3.00%	9.00%
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Percent	0	0	1.52
Effective Income Tax Rate Reconciliation, Tax Expense (Benefit), Share-based Payment Arrangement, Percent	19.00%	(43.00%)	(24.00%)
Effective Income Tax Rate Reconciliation, Acquisition Cost, Percent	0.00%	4.00%	0.00%
Effective Income Tax Rate Reconciliation, Officers' Compensation, Percent	(7.00%)	3.00%	1.00%
Effective Income Tax Rate Reconciliation, Interest, Percent	(10.00%)	1.00%	0.00%
State and local taxes, net of federal benefit	13.00%	12.00%	5.00%
International tax (reflects effect of losses for which tax benefit not realized)	(9.00%)	4.00%	(4.00%)
Effective Income Tax Rate Reconciliation, Tax Contingency, Percent	2.00%	2.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Research, Percent	1.00%	(2.00%)	(2.00%)
Valuation reserve for income taxes and other	0.00%	0.00%	(3.00%)
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent	0.00%	0.00%	3.00%
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	(2.00%)	(3.00%)	2.00%
Effective tax rate	25.00%	2.00%	174.00%