Investment Securities Taxable and Nontaxable Interest Income by Investment Type (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Noninterest Income	$ 24,502	$ 27,161	$ 52,596	$ 53,037
Taxable [Member]
Noninterest Income	21,067	23,816	45,801	46,252
Nontaxable [Member]
Noninterest Income	3,435	3,345	6,795	6,785
Held-to-maturity Securities [Member]
Noninterest Income	6,528	7,846	13,192	15,820
Held-to-maturity Securities [Member] | Taxable [Member]
Noninterest Income	3,721	5,012	7,549	10,085
Held-to-maturity Securities [Member] | Nontaxable [Member]
Noninterest Income	2,807	2,834	5,643	5,735
Available-for-sale Securities [Member]
Noninterest Income	17,408	19,028	38,356	36,740
Available-for-sale Securities [Member] | Taxable [Member]
Noninterest Income	16,780	18,517	37,204	35,690
Available-for-sale Securities [Member] | Nontaxable [Member]
Noninterest Income	628	511	1,152	1,050
Trading Securities [Member]
Noninterest Income	566	287	1,048	477
Trading Securities [Member] | Taxable [Member]
Noninterest Income	566	287	1,048	477
Trading Securities [Member] | Nontaxable [Member]
Noninterest Income	$ 0	$ 0	$ 0	$ 0