CONSOLIDATED STATEMENTS OF CASH FLOWS	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Cash flows from operating activities:
Net income	$ 194,244,000	$ 147,951,000	$ 114,965,000
Adjustments to reconcile net income to cash provided by operating activities:
Provision for credit losses	3,200,000	4,726,000	13,220,000
Depreciation and amortization	8,466,000	6,166,000	6,859,000
Stock-based compensation	17,930,000	12,465,000	7,699,000
Excess tax benefit of stock-based compensation	(5,874,000)	(4,194,000)	(1,552,000)
Deferred income taxes	3,254,000	(7,182,000)	(13,717,000)
Amortization of net premiums for investment securities	9,775,000	8,035,000	9,727,000
Accretion And Amortization Fair Market Value Adjustments Relating To Acquisitions of Loans	(17,144,000)	(17,014,000)	(10,917,000)
Accretion and Amortization Fair Market Value Adjustments Relating to Acquisitions of Other Assets and Liabilities	1,279,000	(552,000)	437,000
Income from bank owned life insurance	(3,899,000)	(4,508,000)	(4,809,000)
Unrealized losses on assets and liabilities measured at fair value, net	(47,000)	(1,212,000)	6,483,000
(Gains) / Losses on:
Sales of investment securities	(615,000)	(757,000)	1,195,000
Business Combination, Bargain Purchase, Gain Recognized, Amount	0	0	(10,044,000)
Gains (Losses) on Extinguishment of Debt	81,000	502,000	1,387,000
Other assets acquired through foreclosure, net	(2,628,000)	(2,866,000)	(5,924,000)
Valuation adjustments of other repossessed assets, net	182,000	294,000	3,743,000
Sale of premises, equipment, and other assets, net	376,000	(2,778,000)	(206,000)
Changes in, net of acquisitions:
Other assets	(9,999,000)	9,242,000	33,185,000
Other liabilities	14,231,000	14,971,000	13,318,000
Net cash provided by operating activities	212,812,000	163,289,000	165,049,000
Investment securities - measured at fair value
Principal pay downs and maturities	347,000	1,144,000	1,881,000
Investment securities - AFS
Purchases	(827,002,000)	(143,052,000)	(729,768,000)
Principal pay downs and maturities	273,950,000	226,455,000	208,228,000
Proceeds from sales	132,546,000	95,826,000	63,153,000
Principal pay downs and maturities of held-to-maturity securities	0	6,600,000	5,375,000
Purchase of investment tax credits	(29,437,000)	(32,484,000)	(40,355,000)
Proceeds from Sale (Payments to Purchase) Investment In Money Market	330,000	2,181,000	(1,968,000)
Proceeds from Life Insurance Policies	797,000	1,046,000	2,582,000
(Purchase) liquidation of restricted stock	(25,821,000)	4,911,000	750,000
Payments for (Proceeds from) Loans and Leases	(1,269,351,000)	(1,560,633,000)	(728,793,000)
Purchase of premises, equipment, and other assets, net	(10,856,000)	(13,925,000)	(18,873,000)
Proceeds from sale of other real estate owned and repossessed assets, net	45,627,000	25,918,000	43,242,000
Cash Acquired from Acquisition	342,427,000	0	21,204,000
Net cash used in investing activities	(1,366,443,000)	(1,386,013,000)	(1,173,342,000)
Cash flows from financing activities:
Net increase in deposits	1,357,855,000	1,093,353,000	1,045,173,000
Proceeds from Issuance of Subordinated Long-term Debt	150,000,000	0	0
Net (increase) decrease in borrowings	(257,038,000)	40,407,000	70,159,000
Payments of Debt Extinguishment Costs	0	(6,501,000)	(10,887,000)
Proceeds from exercise of common stock options	1,935,000	8,294,000	4,595,000
Redemption Of Preferred Stock	(70,500,000)	(70,500,000)	0
Excess tax benefit of stock-based compensation	5,874,000	4,194,000	1,552,000
Cash dividends paid on preferred stock	(750,000)	(1,387,000)	(1,410,000)
Proceeds from Issuance of Common Stock	28,288,000	13,746,000	0
Net cash provided by financing activities	1,213,875,000	1,081,606,000	1,109,182,000
Net increase (decrease) in cash and cash equivalents	60,244,000	(141,118,000)	100,889,000
Cash and cash equivalents at beginning of period	164,396,000	305,514,000	204,625,000
Cash and cash equivalents at end of period	224,640,000	164,396,000	305,514,000
Cash paid during the period for:
Interest	28,831,000	26,516,000	28,613,000
Income taxes	54,590,000	35,556,000	19,105,000
Non-cash investing and financing activity:
Transfers to other assets acquired through foreclosure, net	28,566,000	13,777,000	24,911,000
Change in unfunded LIHTC and SBIC commitments	39,617,000	9,798,000	50,000,000
Non-cash assets acquired in acquisition	1,587,186,000	0	410,827,000
Non-cash liabilities acquired in acquisition	1,764,996,000	0	421,987,000
Change in unrealized gain on AFS securities, net of tax	(6,502,000)	29,209,000	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	(4,276,000)
Change in unfunded obligations	(27,325,000)	(28,522,000)	(29,755,000)
Transfer of HTM securities to AFS, amortized cost	0	275,300,000	0
Unrealized gain on transfer of HTM securities to AFS, net of tax	0	$ 8,976,000	$ 0
Subordinated Debt [Member]
Cash flows from financing activities:
Proceeds from Debt, Net of Issuance Costs	$ 148,211,000