Mortgage Loans - Allowance for Credit Losses for Mortgage Loans (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 19,160
Ending balance	59,445
Commercial loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	19,160
Provision	29,069
Ending balance	59,445
Commercial loans | Balance as of January 1, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 11,216