Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 52,646,000	$ 59,186,000	$ (2,504,000)
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Amortization of deferred loan origination fees, net of costs	3,529,000	3,509,000	3,396,000
Amortization of fair value premiums, net of discounts, on acquired loans	8,000	39,000	3,106,000
Amortization of investment securities premiums, net of accretion of discounts	7,865,000	8,540,000	12,109,000
Amortization of core deposit and customer relationship intangibles	1,473,000	1,677,000	1,906,000
Amortization of fair value premium of acquired deposits	0	340,000	660,000
FDIC Loss Share (Benefit) Expense	(1,403,000)	13,581,000	42,808,000
Other Than Temporary Impairment on securities included in net income	0	0	1,490,000
Depreciation and amortization of premises and equipment	8,986,000	9,420,000	11,100,000
Deferred income taxes, net	(3,658,000)	23,226,000	(37,329,000)
Provision for loan and lease losses, net	113,139,000	65,076,000	161,501,000
Stock-based compensation	1,109,000	1,270,000	1,637,000
Stock-based compensation excess tax benefit recognized in income	(99,000)	0	0
(Gain) loss on:
Sale of securities	(6,896,000)	(12,207,000)	(2,572,000)
Sale of mortgage loans held for sale	(955,000)	(1,570,000)	(3,135,000)
Derivatives	(103,000)	181,000	(81,000)
Early extinguishment of debt	80,000	12,000,000	0
Foreclosed real estate	4,964,000	11,934,000	33,998,000
Sale of other repossessed asset	57,000	(1,623,000)	4,828,000
Sale of premises and equipment	(539,000)	12,000	192,000
Originations of loans held-for-sale	(116,020,000)	(179,430,000)	(211,352,000)
Proceeds from sale of loans held-for-sale	75,637,000	69,862,000	102,383,000
Net (increase) decrease in:
Trading securities	156,000	(59,000)	1,306,000
Accrued interest receivable	(29,742,000)	410,000	708,000
Servicing Assets	(37,000)	2,403,000	(610,000)
Other assets	13,675,000	(7,941,000)	(14,849,000)
Net increase (decrease) in:
Accrued interest on deposits and borrowings	(937,000)	(862,000)	(250,000)
Net increase (decrease) in accrued expenses and other liabilities	28,431,000	4,344,000	(14,584,000)
Net cash provided by operating activities	151,440,000	78,512,000	97,082,000
Purchases of:
Investment securities available-for-sale	(182,054,000)	(119,544,000)	(1,939,000)
Investment securities held-to-maturity	0	(86,478,000)	(499,317,000)
FHLB stock	(31,950,000)	(20,421,000)	0
Maturities and Redemptions of [Abstract]
Maturities and redemptions of investment securities available-for-sale	105,169,000	145,512,000	238,003,000
Investments securities held-to-maturity	88,726,000	101,965,000	39,310,000
FHLB Stock	28,748,000	30,411,000	386,000
Proceeds from sale of:
Investment securities available for sale	256,996,000	300,483,000	103,831,000
Foreclosed real estate and other repossessed assets, including write-offs	40,051,000	47,507,000	117,050,000
Proceeds From Sale And Collection of Loans Held for Sale	0	123,137,000	0
Gain (Loss) on Sale of Property Plant Equipment	(569,000)	(48,000)	0
Proceeds From Sale Of Mortgage Servicing Rights MSR	0	0	5,927,000
Origination and purchase of loans, excluding loans held-for-sale	(801,766,000)	(768,353,000)	(802,572,000)
Principal repayment of loans, including covered loans	699,409,000	817,199,000	861,891,000
(Repayment to) reimbursement to the FDIC for the termination of shared-loss agreements	(10,125,000)	1,573,000	90,697,000
Additions to premises and equipment	(6,469,000)	(5,297,000)	(5,283,000)
Net change in restricted cash	0	(319,000)	(5,058,000)
Net cash provided by investing activities	187,304,000	568,061,000	153,042,000
Net increase (decrease) in:
Deposits	125,991,000	(61,078,000)	(198,052,000)
Securities sold under agreements to repurchase	(459,815,000)	(292,264,000)	(45,315,000)
FHLB advances, federal funds purchased, and other borrowings	(5,741,000)	(228,633,000)	(4,155,000)
Subordinated capital notes	0	(66,550,000)	1,049,000
Exercise of stock options and restricted unit lapsed, net	0	(315,000)	204,000
Purchase of treasury stock	0	0	(8,950,000)
Dividends paid on preferred stock	(13,862,000)	(13,862,000)	(13,862,000)
Dividends paid on common stock	(10,553,000)	(10,141,000)	(17,761,000)
Net cash used in financing activities	(363,980,000)	(672,843,000)	(286,842,000)
Net change in cash and cash equivalents	(25,236,000)	(26,270,000)	(36,718,000)
Cash and cash equivalents at beginning of period	510,439,000	536,709,000	573,427,000
Cash and cash equivalents at end of period	485,203,000	510,439,000	536,709,000
Supplemental Cash Flow Disclosure and Schedule of Non-cash Activities:
Interest paid net	40,570,000	56,302,000	67,766,000
Income Taxes Paid	30,000	10,051,000	13,966,000
Mortgage loans securitized into mortgage-backed securities	74,919,000	112,071,000	116,319,000
Transfer from loans to foreclosed real estate and other repossessed assets	43,163,000	45,538,000	67,345,000
Reclassification of loans held-for-investment portfolio to held-for-sale portfolio	33,647,000	123,137,000	3,445,000
Reclassification of loans held-for-sale portfolio to investment portfolio	293,000	182,000	156,000
Financed sales of foreclosed real estate	1,113,000	2,212,000	4,760,000
Loans booked under GNMA buy-back option	8,268,000	9,681,000	7,945,000
Interest capitalized on loans subject to the temporary payment moratorium	$ 39,701,000	$ 0	$ 0