Accumulated Other Comprehensive Income (Loss) - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassification Adjustments out of Accumulated Other Comprehensive Income [Line Items]
Other income - net realized gains on sales of available for sale securities	$ 1,115	$ 910	$ 2,047	$ 2,335
Interest expense - subordinated debentures and term loans	(1,666)	(1,661)	(4,996)	(4,950)
Income tax expense	(6,557)	(5,980)	(21,247)	(16,485)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	17,067	16,122	51,207	44,902
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	490	360	633	834
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	1,115	910	2,047	2,335
Income tax expense	(390)	(318)	(716)	(817)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	725	592	1,331	1,518
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	(362)	(356)	(1,074)	(1,051)
Income tax expense	127	124	376	367
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	$ (235)	$ (232)	$ (698)	$ (684)