Variable Interest Entities (Narrative) (Details) - USD ($)	Jul. 26, 2010	Dec. 31, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Carrying Amount		$ 289,700,000	$ 360,200,000
Total Maximum exposure to loss in non-consolidated VIEs		1,345,100,000	1,795,200,000
Agency Mortgage-Backed Securitizations [Member]
Variable Interest Entity [Line Items]
Carrying Amount		3,359,100,000	3,186,900,000
Nonagency Mortgage- And Asset-Backed Securitizations [Member]
Variable Interest Entity [Line Items]
Carrying Amount		630,500,000	1,120,000,000
SBI USA Fund [Member]
Variable Interest Entity [Line Items]
Maximum amount committed to invest as per agreement	$ 75,000,000.0
Commitment funded		64,600,000	60,100,000
Carrying amount of equity investment		26,200,000	43,100,000
JEP IV [Member]
Variable Interest Entity [Line Items]
Carrying amount of equity investment		1,100,000	$ 1,200,000
Energy Partners I Lp [Member]
Variable Interest Entity [Line Items]
Carrying Amount		11,000
Total Maximum exposure to loss in non-consolidated VIEs		$ 3,000,000