Fair Value - Impaired Loans Held-for-investment - Tabular Disclosure (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Impaired Loans Held-for-investment
Impaired loans held-for-investment	$ 15,140	$ 2,774
Carried at fair value
Impaired Loans Held-for-investment
Impaired loans held-for-investment	7,646	651
Specific valuation allowance	(6,944)	(290)
Impaired loans held-for-investment carried at fair value, net	702	361
Portion carried at cost
Impaired Loans Held-for-investment
Impaired loans held-for-investment	$ 7,494	$ 2,123