Investment Securities (Mortgage-backed, Asset-backed Securities) (Details)	9 Months Ended
	Sep. 30, 2012
Commercial Mortgage Backed Securities Fixed Rate [Member]
Investment securities
Average basis points of subordination (as a percent)	25.0000
Commercial Mortgage Backed Securities Floating Rate [Member]
Investment securities
Average basis points of subordination (as a percent)	50.0000
Maximum | Commercial Mortgage Backed Securities [Member]
Investment securities
Percentage of underlying loans reported as non-performing	1.00%