Note 2 - Acquisitions (Details) - Assets Acquired and Liabilities Assumed - USD ($) $ in Thousands	Feb. 27, 2015	Jun. 30, 2015	Dec. 31, 2014
Deposits:
Goodwill		$ 314,282	$ 108,095
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	31,024
Bank owned life insurance	16,972
Core deposit intangible	14,556
Other assets	13,860
Total assets acquired	1,065,541
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	19,780
Accrued interest and other liabilities	8,128
Total liabilities assumed	948,973
Total liabilities and equity assumed	948,973
Net assets acquired	116,568
Purchase price	212,176
Goodwill	95,608
Liberty Bancshares, Inc. [Member] | Cost Acquired [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
Liberty Bancshares, Inc. [Member] | Fair Value Adjustments [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	(3,215)
Core deposit intangible	13,857
Other intangibles	(3,063)
Other assets	(3,843)
Total assets acquired	3,974
Deposits:
FHLB borrowings	223
Subordinated debentures	(840)
Accrued interest and other liabilities	300
Total liabilities assumed	(317)
Equity	(112,277)
Total liabilities and equity assumed	(112,594)
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	7,367
Other assets	11,474
Total assets acquired	1,915,190
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	21,244
Accrued interest and other liabilities	9,370
Total liabilities assumed	1,727,300
Total liabilities and equity assumed	1,727,300
Net assets acquired	187,890
Purchase price	299,204
Goodwill	111,314
Delta Trust [Member] | Cost Acquired [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
Delta Trust [Member] | Fair Value Adjustments [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	3,667
Total assets acquired	(3,135)
Deposits:
Time deposits	849
Total deposits	849
FHLB borrowings	1,347
Subordinated debentures	(510)
Accrued interest and other liabilities	601
Total liabilities assumed	2,287
Equity	(193,312)
Total liabilities and equity assumed	(191,025)
Goodwill	$ (100)