Accumulated Other Comprehensive Income (Loss) - Reclassifications (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Other income - net realized gains on sales of available for sale securities	$ 910		$ 2,335	$ 487
Interest expense - subordinated debentures and term loans	(1,661)	(731)	(4,950)	(2,189)
Other expenses - salaries and employee benefits	(24,173)	(20,616)	(72,904)	(61,943)
Income tax expense	(5,862)	(2,667)	(15,873)	(11,490)
NET INCOME	16,122	10,403	44,902	33,083
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) for the Period
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
NET INCOME	360	(208)	834	(851)
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) for the Period | Unrealized gains (losses) on available for sale securities
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Other income - net realized gains on sales of available for sale securities	910		2,335	487
Income tax expense	(318)		(817)	(170)
NET INCOME	592	0	1,518	317
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) for the Period | Unrealized gains (losses) on cash flow hedges
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Interest expense - subordinated debentures and term loans	(356)	(207)	(1,051)	(587)
Income tax expense	124	72	367	205
NET INCOME	(232)	(135)	(684)	(382)
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) for the Period | Unrealized gains (losses) on defined benefit plans
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Other expenses - salaries and employee benefits		(112)		(1,209)
Income tax expense		39		423
NET INCOME	$ 0	$ (73)	$ 0	$ (786)