Note 2 - Acquisitions (Details) - Assets Acquired and Liabilities Assumed (USD $) In Thousands, unless otherwise specified	0 Months Ended
	Feb. 27, 2015	Mar. 31, 2015	Dec. 31, 2014
Deposits:
Goodwill		$ 314,643	$ 108,095
Cost Acquired [Member] | Liberty Bancshares, Inc. [Member]
Note 2 - Acquisitions (Details) - Assets Acquired and Liabilities Assumed [Line Items]
Cash and due from banks	102,637
Federal funds sold	7,060
Investment securities	99,123
Loans acquired, not covered by FDIC loss share	790,493
Allowance for loan losses	(10,422)
Premises and equipment	34,239
Bank owned life insurance	16,972
Core deposit intangible	699
Other intangibles	3,063
Other assets	17,703
Total assets acquired	1,061,567
Deposits:
Non-interest bearing transaction accounts	146,618
Interest bearing transaction accounts and savings deposits	543,183
Time deposits	184,913
Total deposits	874,714
FHLB borrowings	46,128
Subordinated debentures	20,620
Accrued interest and other liabilities	7,828
Total liabilities assumed	949,290
Equity	112,277
Total liabilities and equity assumed	1,061,567
Cost Acquired [Member] | Delta Trust [Member]
Note 2 - Acquisitions (Details) - Assets Acquired and Liabilities Assumed [Line Items]
Cash and due from banks	39,848
Federal funds sold	76,508
Investment securities	570,199
Loans acquired, not covered by FDIC loss share	1,163,398
Allowance for loan losses	(14,635)
Foreclosed assets not covered by FDIC loss share	747
Premises and equipment	44,837
Bank owned life insurance	22,149
Deferred tax asset	3,700
Other assets	11,474
Total assets acquired	1,918,325
Deposits:
Non-interest bearing transaction accounts	103,825
Interest bearing transaction accounts and savings deposits	995,207
Time deposits	436,181
Total deposits	1,535,213
Federal funds purchased and securities sold under agreement to repurchase	16,230
FHLB borrowings	143,047
Subordinated debentures	21,754
Accrued interest and other liabilities	8,769
Total liabilities assumed	1,725,013
Equity	193,312
Total liabilities and equity assumed	1,918,325
Goodwill	100
Fair Value Adjustments [Member] | Liberty Bancshares, Inc. [Member]
Note 2 - Acquisitions (Details) - Assets Acquired and Liabilities Assumed [Line Items]
Cash and due from banks	(14)
Investment securities	(335)
Loans acquired, not covered by FDIC loss share	(9,835)
Allowance for loan losses	10,422
Premises and equipment	(1,229)
Core deposit intangible	13,857
Other intangibles	(3,063)
Other assets	(4,293)
Total assets acquired	5,510
Deposits:
FHLB borrowings	223
Accrued interest and other liabilities	300
Total liabilities assumed	523
Equity	(112,277)
Total liabilities and equity assumed	(111,754)
Fair Value Adjustments [Member] | Delta Trust [Member]
Note 2 - Acquisitions (Details) - Assets Acquired and Liabilities Assumed [Line Items]
Investment securities	(3,381)
Loans acquired, not covered by FDIC loss share	(26,855)
Allowance for loan losses	14,635
Premises and equipment	(2,794)
Core deposit intangible	11,273
Other intangibles	420
Deferred tax asset	3,866
Total assets acquired	(2,936)
Deposits:
Time deposits	849
Total deposits	849
FHLB borrowings	1,347
Accrued interest and other liabilities	601
Total liabilities assumed	2,797
Equity	(193,312)
Total liabilities and equity assumed	(190,515)
Goodwill	(100)
Liberty Bancshares, Inc. [Member]
Note 2 - Acquisitions (Details) - Assets Acquired and Liabilities Assumed [Line Items]
Cash and due from banks	102,623
Federal funds sold	7,060
Investment securities	98,788
Loans acquired, not covered by FDIC loss share	780,658
Premises and equipment	33,010
Bank owned life insurance	16,972
Core deposit intangible	14,556
Other assets	13,410
Total assets acquired	1,067,077
Deposits:
Non-interest bearing transaction accounts	146,618
Interest bearing transaction accounts and savings deposits	543,183
Time deposits	184,913
Total deposits	874,714
FHLB borrowings	46,351
Subordinated debentures	20,620
Accrued interest and other liabilities	8,128
Total liabilities assumed	949,813
Total liabilities and equity assumed	949,813
Net assets acquired	117,264
Purchase price	212,176
Goodwill	94,912
Delta Trust [Member]
Note 2 - Acquisitions (Details) - Assets Acquired and Liabilities Assumed [Line Items]
Cash and due from banks	39,848
Federal funds sold	76,508
Investment securities	566,818
Loans acquired, not covered by FDIC loss share	1,136,543
Foreclosed assets not covered by FDIC loss share	747
Premises and equipment	42,043
Bank owned life insurance	22,149
Core deposit intangible	11,273
Other intangibles	420
Deferred tax asset	7,566
Other assets	11,474
Total assets acquired	1,915,389
Deposits:
Non-interest bearing transaction accounts	103,825
Interest bearing transaction accounts and savings deposits	995,207
Time deposits	437,030
Total deposits	1,536,062
Federal funds purchased and securities sold under agreement to repurchase	16,230
FHLB borrowings	144,394
Subordinated debentures	21,754
Accrued interest and other liabilities	9,370
Total liabilities assumed	1,727,810
Total liabilities and equity assumed	1,727,810
Net assets acquired	187,580
Purchase price	299,204
Goodwill	$ 111,624