Note 17 - Fair Value Measurements - Estimated Fair Values and Related Carrying Amounts of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financial assets:
Held-to-maturity securities	$ 373,298	$ 465,960
Reported Value Measurement [Member]
Financial assets:
Cash and cash equivalents	598,042	285,659
Interest bearing balances due from banks - time	3,314	4,563
Held-to-maturity securities	368,058	462,096
Mortgage loans held for sale	24,038	27,788
Interest receivable	43,528	27,788
Financial liabilities:
Federal funds purchased and securities sold under agreements to repurchase	122,444	115,029
Other borrowings	1,380,024	273,159
Subordinated debentures	140,565	60,397
Interest payable	4,564	1,668
Reported Value Measurement [Member] \| Non-Interest Bearing Transaction Accounts [Member]
Financial liabilities:
Deposits	2,665,249	1,491,676
Reported Value Measurement [Member] \| Interest Bearing Transaction Accounts and Savings Deposits [Member]
Financial liabilities:
Deposits	6,494,896	3,956,483
Reported Value Measurement [Member] \| Time Deposits [Member]
Financial liabilities:
Deposits	1,932,730	1,287,060
Reported Value Measurement [Member] \| Legacy Loans [Member]
Financial assets:
Legacy loans (net of allowance)	5,663,941	4,290,921
Reported Value Measurement [Member] \| Acquired Loans [Member]
Financial assets:
Legacy loans (net of allowance)	5,074,076	1,305,683
Estimate of Fair Value Measurement [Member]
Financial assets:
Cash and cash equivalents	598,042	285,659
Interest bearing balances due from banks - time	3,314	4,563
Held-to-maturity securities	373,298	465,960
Mortgage loans held for sale	24,038	27,788
Interest receivable	43,528	27,788
Financial liabilities:
Federal funds purchased and securities sold under agreements to repurchase	122,444	115,029
Other borrowings	1,381,365	292,367
Subordinated debentures	136,474	55,318
Interest payable	4,564	1,668
Estimate of Fair Value Measurement [Member] \| Non-Interest Bearing Transaction Accounts [Member]
Financial liabilities:
Deposits	2,665,249	1,491,676
Estimate of Fair Value Measurement [Member] \| Interest Bearing Transaction Accounts and Savings Deposits [Member]
Financial liabilities:
Deposits	6,494,896	3,956,483
Estimate of Fair Value Measurement [Member] \| Time Deposits [Member]
Financial liabilities:
Deposits	1,915,539	1,278,339
Estimate of Fair Value Measurement [Member] \| Legacy Loans [Member]
Financial assets:
Legacy loans (net of allowance)	5,646,505	4,305,165
Estimate of Fair Value Measurement [Member] \| Acquired Loans [Member]
Financial assets:
Legacy loans (net of allowance)	5,058,455	1,310,017
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Financial assets:
Cash and cash equivalents	598,042	285,659
Interest bearing balances due from banks - time
Held-to-maturity securities
Mortgage loans held for sale
Interest receivable
Financial liabilities:
Federal funds purchased and securities sold under agreements to repurchase
Other borrowings
Subordinated debentures
Interest payable
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member] \| Non-Interest Bearing Transaction Accounts [Member]
Financial liabilities:
Deposits
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member] \| Interest Bearing Transaction Accounts and Savings Deposits [Member]
Financial liabilities:
Deposits
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member] \| Time Deposits [Member]
Financial liabilities:
Deposits
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member] \| Legacy Loans [Member]
Financial assets:
Legacy loans (net of allowance)
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member] \| Acquired Loans [Member]
Financial assets:
Legacy loans (net of allowance)
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Financial assets:
Cash and cash equivalents
Interest bearing balances due from banks - time	3,314	4,563
Held-to-maturity securities	373,298	465,960
Mortgage loans held for sale
Interest receivable	43,528	27,788
Financial liabilities:
Federal funds purchased and securities sold under agreements to repurchase	122,444	115,029
Other borrowings	1,381,365	292,367
Subordinated debentures	136,474	55,318
Interest payable	4,564	1,668
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member] \| Non-Interest Bearing Transaction Accounts [Member]
Financial liabilities:
Deposits	2,665,249	1,491,676
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Bearing Transaction Accounts and Savings Deposits [Member]
Financial liabilities:
Deposits	6,494,896	3,956,483
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member] \| Time Deposits [Member]
Financial liabilities:
Deposits
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member] \| Legacy Loans [Member]
Financial assets:
Legacy loans (net of allowance)
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member] \| Acquired Loans [Member]
Financial assets:
Legacy loans (net of allowance)
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Financial assets:
Cash and cash equivalents
Interest bearing balances due from banks - time
Held-to-maturity securities
Mortgage loans held for sale	24,038	27,788
Interest receivable
Financial liabilities:
Federal funds purchased and securities sold under agreements to repurchase
Other borrowings
Subordinated debentures
Interest payable
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member] \| Non-Interest Bearing Transaction Accounts [Member]
Financial liabilities:
Deposits
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member] \| Interest Bearing Transaction Accounts and Savings Deposits [Member]
Financial liabilities:
Deposits
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member] \| Time Deposits [Member]
Financial liabilities:
Deposits	1,915,539	1,278,339
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member] \| Legacy Loans [Member]
Financial assets:
Legacy loans (net of allowance)	5,646,505	4,305,165
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member] \| Acquired Loans [Member]
Financial assets:
Legacy loans (net of allowance)	$ 5,058,455	$ 1,310,017

Represents the fair value portion of interest bearing balances due from banks - time.

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- Definition

Fair value portion of interest payable on debt, including, but not limited to, trade payables.

+ References

No definition available.

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The fair value of accrued interest receivable.

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No definition available.

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- Definition

The fair value portion of the aggregate of other miscellaneous borrowings owed by the reporting entity as of the balance sheet date.

+ References

No definition available.

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- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

No definition available.

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- Definition

Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

+ References

No definition available.

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- Definition

Fair value of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Fair value portion of short term borrowing where a bank borrows, at the federal funds rate, from another bank and securities that an entity sells and agrees to repurchase at a specified date for a specified price.

+ References

No definition available.

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- References

No definition available.

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- References

No definition available.

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- Definition

Fair value of investments in debt securities classified as held-to-maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

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Balance Type:	debit
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- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

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- Definition

Fair value portion of mortgage loans held-for-sale.

+ References

No definition available.

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