Investment Securities Taxable and Nontaxable Interest Income by Investment Type (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Noninterest Income	$ 47,364	$ 27,473
Taxable [Member]
Noninterest Income	42,683	23,958
Nontaxable [Member]
Noninterest Income	4,681	3,515
Held-to-maturity Securities [Member]
Noninterest Income	5,330	6,454
Held-to-maturity Securities [Member] | Taxable [Member]
Noninterest Income	2,604	3,592
Held-to-maturity Securities [Member] | Nontaxable [Member]
Noninterest Income	2,726	2,862
Available-for-sale Securities [Member]
Noninterest Income	41,562	20,421
Available-for-sale Securities [Member] | Taxable [Member]
Noninterest Income	39,607	19,768
Available-for-sale Securities [Member] | Nontaxable [Member]
Noninterest Income	1,955	653
Trading Securities [Member]
Noninterest Income	472	598
Trading Securities [Member] | Taxable [Member]
Noninterest Income	472	598
Trading Securities [Member] | Nontaxable [Member]
Noninterest Income	$ 0	$ 0