Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income:
Loans	$ 312,421	$ 321,945	$ 367,622
Mortgage-backed securities	26,994	30,522	35,338
Investment securities	6,232	4,125	3,608
Total interest income	345,647	356,592	406,568
Interest expense:
Deposits	30,298	29,253	27,034
Securities sold under agreements to repurchase	7,223	18,805	29,567
Advances from FHLB and other borrowings	2,398	6,186	9,072
Subordinated capital notes	1,556	2,921	3,523
Total interest expense	41,475	57,165	69,196
Net interest income	304,172	299,427	337,372
Provision for Loan, Lease, and Other Losses	113,139	65,076	161,501
Net interest income after provision for loan and lease losses	191,033	234,351	175,871
Non-interest income:
Banking service revenues	39,468	41,647	41,466
Wealth management revenue	25,790	27,433	29,040
Mortgage banking activities	4,050	5,021	6,128
Total Banking and Financial Service Revenues	69,308	74,101	76,634
Net impairment losses recognized in earnings	0	0	1,490
FDIC shared-loss benefit (expense), net [Abstract]
FDIC shared-loss benefit (expense), net	1,403	(13,581)	(42,808)
Reimbursement from FDIC shared-loss coverage in sale of loans	0	0	20,000
Net gain (loss) on:
Sale of securities	6,896	12,207	2,572
Derivatives	132	(71)	(190)
Early extinguishment of debt	(80)	(12,000)	0
Other non-interest income	1,028	6,163	(2,142)
Total non-interest income, net	78,687	66,819	52,576
Non-interest expense:
Compensation and employee benefits	79,751	76,761	78,999
Professional and service fees	12,406	12,235	14,973
Occupancy and equipment	32,557	30,300	33,466
Insurance	5,223	9,109	9,567
Electronic banking charges	19,322	20,707	21,893
Information technology related expenses	8,010	7,116	5,648
Advertising, business promotion, and strategic initiatives	5,616	5,485	6,452
Loss on sale of foreclosed real estate and other reossessed assets	4,634	10,282	30,546
Loan servicing and clearing expenses	4,693	8,247	9,198
Taxes, other than payroll and income taxes	9,187	9,782	9,460
Communication	3,415	3,379	3,808
Printing, postage, stationary and supplies	2,437	2,558	2,575
Director and investors relations	1,072	1,087	1,091
Credit related expenses	7,992	10,267	11,091
Other	5,316	8,675	9,738
Total non-interest expense	201,631	215,990	248,505
Income before income taxes	68,089	85,180	(20,058)
Income tax expense (benefit)	15,443	25,994	(17,554)
Net income	52,646	59,186	(2,504)
Dividends on preferred stock	(13,862)	(13,862)	(13,862)
Income (loss) available to common shareholders	$ 38,784	$ 45,324	$ (16,366)
Earnings per common share:
Basic	$ 0.88	$ 1.03	$ (0.37)
Diluted	$ 0.88	$ 1.03	$ (0.37)
Average common shares outstanding and equivalents	51,096	51,088	51,455
Cash dividends per share of common stock	$ 0.24	$ 0.24	$ 0.36