Investment Securities (Weighted-Average Expected Maturity of Mortgage and Other Asset-Backed Debt Securities) (Details)	6 Months Ended
	Jun. 30, 2013
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Agency [Member]
Mortgage And Other Asset Backed Securities [Line Items]
Weighted average expected maturity	4 years 7 months
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member]
Mortgage And Other Asset Backed Securities [Line Items]
Weighted average expected maturity	5 years 11 months
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Agency [Member]
Mortgage And Other Asset Backed Securities [Line Items]
Weighted average expected maturity	4 years 2 months
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Non-agency [Member]
Mortgage And Other Asset Backed Securities [Line Items]
Weighted average expected maturity	2 years 5 months
Asset backed [Member]
Mortgage And Other Asset Backed Securities [Line Items]
Weighted average expected maturity	3 years 10 months