Investment Securities (Weighted-Average Expected Maturity of Mortgage and Other Asset-Backed Debt Securities) (Details)	6 Months Ended
	Jun. 30, 2011
Non-Agency Mortgage-Backed Securities [Member]
Weighted average expected maturity	4.7
Agency Mortgage-Backed Securities [Member]
Weighted average expected maturity	4.4
Commercial Mortgage-backed Agency [Member]
Weighted average expected maturity	4.6
Commercial Mortgage-backed Non-agency [Member]
Weighted average expected maturity	2.9
Asset backed [Member]
Weighted average expected maturity	3.2