Accumulated Other Comprehensive Income (Loss) - Reclassifications (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Other income - net realized gains on sales of available for sale securities	$ 1,025	$ 581
Income tax expense	(5,834)	(4,617)
Interest expense - subordinated debentures and term loans	(1,660)	(1,641)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	16,172	13,620
Amount Reclassified from Accumulated Other Comprehensive Income (Loss) for the Period
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	436	154
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	1,025	581
Income tax expense	(359)	(203)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	666	378
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]
Income tax expense	124	120
Interest expense - subordinated debentures and term loans	(354)	(344)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	$ (230)	$ (224)