Variable Interest Entities (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2016 USD ($) trust	Jun. 30, 2016 USD ($) item	Dec. 31, 2015 USD ($)
Variable interest entities
VIE Assets		$ 80,076,117	$ 76,675,689
VIE Liabilities		79,087,142	75,817,014
Investment securities		898,803	724,947
Interest in VIE		200,541	$ 199,201
Primary beneficiary
Variable interest entities
VIE Assets		140,200
VIE Liabilities		$ 62,200
Primary beneficiary | Accounting Standards Update 2015-02 | Adjustment
Variable interest entities
Number of VIE's | trust	14
VIE Assets	$ 15,100,000
VIE Liabilities	15,100,000
Not primary beneficiary
Variable interest entities
Number of CDO structures currently in default | item		1
Maximum risk of loss related to VIEs, on fair value basis		$ 114,300
Not primary beneficiary | Accounting Standards Update 2015-02 | Adjustment
Variable interest entities
Maximum risk of loss related to VIEs, on fair value basis		131,400
Interest in VIE		131,400
Commitments on loss		29,200
Not primary beneficiary | Securitization SPEs
Variable interest entities
Debt obligations to beneficial interest holders, unpaid principal balances		$ 21,800,000
CMBS | Primary beneficiary | Accounting Standards Update 2015-02 | Adjustment
Variable interest entities
Investment securities	$ 120,900