Fair Value Disclosures (Analysis of Level 3 Assets and Liabilities Narrative) (Details) - USD ($) $ in Thousands	10 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	$ 82,400	$ 236,700	$ 139,000
Transfers of assets from Level 3 to Level 2	55,900	85,800	54,600
Transfers of liabilities from Level 3 to Level 2	100
Transfers of liabilities from Level 2 to Level 3	0
Net gains (losses) on Level 3 assets (realized and unrealized)	(3,400)	455,500	(24,800)
Net gains (losses) on Level 3 liabilities (realized and unrealized)	(5,800)	7,600	(14,900)
Excluded assets from unobservable quantitative information		280,600	137,800
Excluded liabilities from unobservable quantitative information		600	300
Other Secured Financings [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 3 to Level 2		51,600
Net gains (losses) on Level 3 liabilities (realized and unrealized)		0	0
Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 3 to Level 2			1,000
Net gains (losses) on Level 3 liabilities (realized and unrealized)	2,959	(163)	0
Derivative Financial Instruments Liabilities Net [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Transfers of liabilities from Level 3 to Level 2			3,300
Collateralized Debt Obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	2,800	69,800	73,000
Transfers of assets from Level 3 to Level 2	600	34,900
Net gains (losses) on Level 3 assets (realized and unrealized)	(2,309)	(66,332)	(6,386)
Non-Agency Residential Mortgage-Backed Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	58,800	30,400	30,300
Transfers of assets from Level 3 to Level 2	45,900	16,300	22,400
Commercial Mortgage Backed Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3		11,300	16,600
Transfers of assets from Level 3 to Level 2	2,200	6,300
Net gains (losses) on Level 3 assets (realized and unrealized)	(4,469)	(3,813)	(4,237)
Municipal securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3		21,500
Net gains (losses) on Level 3 assets (realized and unrealized)		10
Other Asset Backed Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	16,400
Transfers of assets from Level 3 to Level 2	1,100
Net gains (losses) on Level 3 assets (realized and unrealized)	(4,535)	(990)	1,784
Loans and Finance Receivables [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	800	20,100	8,500
Transfers of assets from Level 3 to Level 2	1,700	4,700	3,500
Net gains (losses) on Level 3 assets (realized and unrealized)	15,008	(14,755)	(31,311)
Corporate Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	200	7,400
Transfers of assets from Level 3 to Level 2	800		7,500
Net gains (losses) on Level 3 assets (realized and unrealized)	(2,454)	(11,013)	6,629
Corporate Equity Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	2,300		9,700
Transfers of assets from Level 3 to Level 2	3,600	7,700	4,900
Net gains (losses) on Level 3 assets (realized and unrealized)	1,551	11,154	957
Investments at Fair Value [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Transfers of assets from Level 2 to Level 3	1,000	74,700
Transfers of assets from Level 3 to Level 2		15,800	15,500
Net gains (losses) on Level 3 assets (realized and unrealized)	$ (1,317)	$ 62,804	$ 17,642