Investment Securities (State And Municipal Obligations, By State And Economic Sector) (Details)	12 Months Ended
	Dec. 31, 2012
Texas
Investment [Line Items]
% of Portfolio	9.90%
Average Life (in years)	5 years 9 months 22 days
Average Rating (Moody’s)	Aa1
Florida
Investment [Line Items]
% of Portfolio	9.40%
Average Life (in years)	5 years 1 month 6 days
Average Rating (Moody’s)	Aa2
Ohio
Investment [Line Items]
% of Portfolio	6.00%
Average Life (in years)	5 years 9 months 22 days
Average Rating (Moody’s)	Aa2
Washington
Investment [Line Items]
% of Portfolio	5.70%
Average Life (in years)	5 years 3 months 19 days
Average Rating (Moody’s)	Aa2
New York
Investment [Line Items]
% of Portfolio	5.20%
Average Life (in years)	7 years 2 months 13 days
Average Rating (Moody’s)	Aa2
General obligation
Investment [Line Items]
% of Portfolio	31.70%
Average Life (in years)	5 years 2 months 13 days
Average Rating (Moody’s)	Aa2
Housing
Investment [Line Items]
% of Portfolio	18.20%
Average Life (in years)	7 years 2 months 13 days
Average Rating (Moody’s)	Aa1
Lease
Investment [Line Items]
% of Portfolio	15.40%
Average Life (in years)	5 years 1 month 6 days
Average Rating (Moody’s)	Aa2
Transportation
Investment [Line Items]
% of Portfolio	13.30%
Average Life (in years)	4 years 9 months 22 days
Average Rating (Moody’s)	Aa3
Limited tax
Investment [Line Items]
% of Portfolio	5.00%
Average Life (in years)	5 years 10 months 28 days
Average Rating (Moody’s)	Aa1