Investment in Loans (Schedule of Commercial Mortgage Loans) (Details) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	$ 1,026,983
Commercial mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	264,932
Premium (Discount)	(27,249)
Amortized Cost	237,683
Gains	2,131
Losses	(191)
Fair Value	$ 239,623
Coupon	8.92%
Yield	9.44%
Life (Years)	347 days