CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
INTEREST AND DIVIDEND INCOME
Loans receivable, including fees	$ 1,059,205	$ 979,394	$ 945,530
Investment securities	44,684	43,846	58,184
Securities purchased under resale agreements	20,323	21,236	20,392
Investment in Federal Home Loan Bank and Federal Reserve Bank stock	6,272	6,869	4,673
Due from banks and short-term investments	23,214	17,340	22,316
Total interest and dividend income	1,153,698	1,068,685	1,051,095
INTEREST EXPENSE
Customer deposit accounts	65,486	63,496	75,895
Federal Home Loan Bank advances	4,116	4,173	6,248
Securities sold under repurchase agreements	38,395	41,381	46,166
Long-term debt	4,823	3,436	3,855
Other borrowings		6	4
Total interest expense	112,820	112,492	132,168
Net interest income before provision for loan losses	1,040,878	956,193	918,927
Provision for loan losses on non-covered loans	44,125	18,336	60,168
Provision for loan losses on covered loans	5,033	4,028	5,016
Net interest income after provision for loan losses	991,720	933,829	853,743
NONINTEREST (LOSS) INCOME
Impairment loss on investment securities			(5,165)
Less: Noncredit-related impairment loss recorded in other comprehensive income			5,066
Net impairment loss on investment securities recognized in earnings			(99)
Changes in FDIC indemnification asset and receivable/payable	(201,417)	(228,585)	(122,251)
Branch fees	37,866	32,036	30,906
Net gains on sales of investment securities	10,851	12,089	757
Letters of credit fees and commissions	25,941	22,116	19,104
Ancillary loan fees	10,616	9,368	8,831
Foreign exchange income	11,381	12,658	7,166
Net gains on sales of loans	39,132	7,750	17,045
Dividend and other investment income	5,464	993	(439)
Other commission and fee income	29,419	20,400	16,349
Other operating income	19,033	18,707	17,013
Total noninterest loss	(11,714)	(92,468)	(5,618)
NONINTEREST EXPENSE
Compensation and employee benefits	231,838	175,906	171,374
Occupancy and equipment expense	63,815	56,641	55,475
Amortization of investments in affordable housing partnerships and other tax credit investments	75,660	27,268	18,058
Amortization of premiums on deposits acquired	10,204	9,365	10,906
Deposit insurance premiums and regulatory assessments	21,922	16,550	14,130
Loan related expenses	3,438	12,520	14,987
Other real estate owned (income) expense	(3,591)	(1,128)	22,349
Legal expense	53,018	31,718	25,441
Data processing	15,888	9,095	9,231
Other operating expenses	92,359	77,576	80,582
Total noninterest expense	564,551	415,511	422,533
INCOME BEFORE TAXES	415,455	425,850	425,592
PROVISION FOR INCOME TAXES	72,972	130,805	143,942
NET INCOME	342,483	295,045	281,650
PREFERRED STOCK DIVIDENDS		3,428	6,857
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	$ 342,483	$ 291,617	$ 274,793
EARNINGS PER SHARE AVAILABLE TO COMMON STOCKHOLDERS
BASIC (in dollars per share)	$ 2.39	$ 2.11	$ 1.92
DILUTED (in dollars per share)	$ 2.38	$ 2.10	$ 1.89
WEIGHTED AVERAGE NUMBER OF SHARES OUTSTANDING
BASIC (in shares)	142,952	137,342	141,457
DILUTED (in shares)	143,563	139,574	147,175
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 0.72	$ 0.60	$ 0.40