Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Basis differences related to financial derivatives	$ 51,177	$ 7,614
Basis differences related to hedged items	0	1,810
Unrealized losses on securities	2,805	0
Allowance for losses	2,650	1,929
Unrealized losses on cash flow hedges	1,491	0
Compensation and benefits	819	967
Stock-based compensation	571	623
Capital loss carryforwards and other-than-temporary impairment	86	36
Other	88	121
Total deferred tax assets	59,601	13,064
Deferred tax liability:
Basis differences related to hedged items	42,940	0
Unrealized gains on securities	0	4,807
Unrealized gains on cash flow hedges	0	1,827
Other	151	61
Total deferred tax liability	43,091	6,695
Net deferred tax asset	16,510	6,369
Capital Loss Carryforward
Deferred tax assets:
Valuation allowance	$ (86)	$ (36)