Investments - Allowance for Credit Loss on Beneficial Interests (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Debt Securities, Available-for-sale, Allowance for Credit Loss, Beginning Balance	$ 0	$ 0
Beginning period adjustment for CECL	(4,221)	0
Provision for credit losses on beneficial interests	(2,987)	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Ending Balance	$ (7,208)	$ 0