Investment Securities, Available-for-Sale (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Investment Securities, Available-for-Sale
Available-for-sale Securities	$ 3,222,829,000	$ 3,683,005,000
Available-for-sale Securities, Gross Unrealized Gain Accumulated In Investments	49,801,000	101,778,000
Investment securities pledged as collateral	1,635,316,000	1,525,400,000
Other-than-temporary impairment on investment securities	0	0
Reclassification of AFS to HTM
Investment Securities, Available-for-Sale
Percent Available-For-Sale Prior to Reclassification	100.00%
Percent Available-For-Sale Subsequent to Reclassification	85.00%
Percent Held-To-Maturity Subsequent to Reclassification	15.00%
State and local governments
Investment Securities, Available-for-Sale
Available-for-sale Securities	1,385,078,000	1,214,518,000
Available-for-sale Securities, Gross Unrealized Gain Accumulated In Investments	31,621,000	88,095,000
State and local governments | Reclassification of AFS to HTM
Investment Securities, Available-for-Sale
Available-for-sale Securities	484,583,000
Available-for-sale Securities, Gross Unrealized Gain Accumulated In Investments	4,624,000
Residential mortgage-backed securities
Investment Securities, Available-for-Sale
Non-guaranteed private label whole loan mortgage-backed securities	2,602,000	46,733,000
Available-for-sale Securities	1,384,622,000	2,160,302,000
Available-for-sale Securities, Gross Unrealized Gain Accumulated In Investments	$ 14,071,000	$ 8,860,000