Fair Value Measures - Reconciliation of Changes in Assets and Liabilities with Unobservable Inputs (Details) - CMBS [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 53,304	$ 58,646
Total gains and losses:
Unrealized loss included in other comprehensive income, net	(2,271)	(977)
Purchases, issuances, settlements and amortization:
Principal payments received	(4,077)	(4,504)
Amortization included in net income	259	139
Ending balance	$ 47,215	$ 53,304