Investment Securities (State And Municipal Obligations, By State And Economic Sector) (Details)	9 Months Ended
	Sep. 30, 2015 yr
Sector Classification, Texas [Member]
Investment [Line Items]
% of Portfolio	12.10%
Average Life (in years)	6.1
Average Rating (Moody's)	Aa2
Sector Classification, Florida [Member]
Investment [Line Items]
% of Portfolio	7.00%
Average Life (in years)	4.5
Average Rating (Moody's)	Aa3
Sector Classification New York [Member]
Investment [Line Items]
% of Portfolio	6.90%
Average Life (in years)	6.8
Average Rating (Moody's)	Aa2
Sector Classification Ohio [Member]
Investment [Line Items]
% of Portfolio	6.70%
Average Life (in years)	6.1
Average Rating (Moody's)	Aa2
Sector Classification, Washington [Member]
Investment [Line Items]
% of Portfolio	5.40%
Average Life (in years)	5.7
Average Rating (Moody's)	Aa2
Sector Classification, General Obligation [Member]
Investment [Line Items]
% of Portfolio	37.70%
Average Life (in years)	5.6
Average Rating (Moody's)	Aa2
Sector Classification, Lease [Member]
Investment [Line Items]
% of Portfolio	18.90%
Average Life (in years)	5.5
Average Rating (Moody's)	Aa2
Sector Classification, Transportation [Member]
Investment [Line Items]
% of Portfolio	12.90%
Average Life (in years)	4.7
Average Rating (Moody's)	A1
Sector Classification Housing [Member]
Investment [Line Items]
% of Portfolio	12.90%
Average Life (in years)	6.4
Average Rating (Moody's)	Aa1
Sector Classification, Limited Tax [Member]
Investment [Line Items]
% of Portfolio	8.90%
Average Life (in years)	6.5
Average Rating (Moody's)	Aa2