Loans and Credit Quality (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	$ 92,378	$ 81,180
Allowance for loan and lease losses	92,378	81,180	84,455	82,034
Allowance for Loan and Lease Losses, Write-offs	(10,490)	(1,550)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	2,542	740
Provision for Loan and Lease Losses	15,871us-gaap_ProvisionForLoanAndLeaseLosses	(44)us-gaap_ProvisionForLoanAndLeaseLosses
Loans and Leases Receivable, Net of Deferred Income	12,272,166	4,161,067	11,882,432
Loans and Leases Receivable Net Of Deferred Income Covered And Noncovered	12,272,166	4,161,067
Mortgage Loans on Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	30,911	24,352
Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	2,173	4,103
Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	45,794	27,740
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	802	3,785
Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance, Covered	12,698	21,200	13,999	21,793
Allowance for Loan and Lease Losses, Write-offs	(579)	0
Allowance for Loan and Lease Loss, Recovery of Bad Debts	11	51
Provision for Loan and Lease Losses	(733)	(644)
Financing Receivable, Allowance for Credit Losses, Acquired with Deteriorated Credit Quality	12,698	21,200
Loans and Leases Receivable, Net of Deferred Income	254,285	332,516	290,791
Financing Receivable, Acquired with Deteriorated Credit Quality	254,285	332,516
NonCovered [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	79,680	59,980	70,456	60,241
Impaired Financing Receivable, Related Allowance	12,226		10,774
Allowance for Loan and Lease Losses, Write-offs	(9,911)	(1,550)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	2,531	689
Provision for Loan and Lease Losses	16,604	600
Financing Receivable, Individually Evaluated for Impairment	12,226	8,665
Financing Receivable, Collectively Evaluated for Impairment	67,454	51,315
Loans and Leases Receivable, Net of Deferred Income	12,017,881	3,828,551	11,591,641
Financing Receivable, Individually Evaluated for Impairment	175,309	93,222
Financing Receivable, Collectively Evaluated for Impairment	11,842,572	3,735,329
NonCovered [Member] \| Mortgage Loans on Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance			25,097	26,078
Impaired Financing Receivable, Related Allowance	1,500		693
Allowance for Loan and Lease Losses, Write-offs	(1,453)	(94)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	1,295	261
Provision for Loan and Lease Losses	5,972	(1,893)
Financing Receivable, Individually Evaluated for Impairment		2,690
Financing Receivable, Collectively Evaluated for Impairment	29,411	21,662
Loans and Leases Receivable, Net of Deferred Income	5,588,430	2,320,554	5,340,560
Financing Receivable, Individually Evaluated for Impairment	59,733	58,532
Financing Receivable, Collectively Evaluated for Impairment	5,528,697	2,262,022
NonCovered [Member] \| Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance			4,248	4,298
Impaired Financing Receivable, Related Allowance			69
Allowance for Loan and Lease Losses, Write-offs	0	0
Allowance for Loan and Lease Loss, Recovery of Bad Debts	632	24
Provision for Loan and Lease Losses	(2,707)	(219)
Financing Receivable, Individually Evaluated for Impairment	55	251
Financing Receivable, Collectively Evaluated for Impairment	2,118	3,852
Loans and Leases Receivable, Net of Deferred Income	328,709	240,073	307,135
Financing Receivable, Individually Evaluated for Impairment	8,639	12,926
Financing Receivable, Collectively Evaluated for Impairment	320,070	227,147
NonCovered [Member] \| Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance			39,858	26,921
Impaired Financing Receivable, Related Allowance			9,975
Allowance for Loan and Lease Losses, Write-offs	(8,395)	(1,441)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	410	377
Provision for Loan and Lease Losses	13,921	1,883
Financing Receivable, Individually Evaluated for Impairment	10,493	5,337
Financing Receivable, Collectively Evaluated for Impairment	35,301	22,403
Loans and Leases Receivable, Net of Deferred Income	6,007,067	1,201,142	5,842,463
Financing Receivable, Individually Evaluated for Impairment	103,208	17,792
Financing Receivable, Collectively Evaluated for Impairment	5,903,859	1,183,350
NonCovered [Member] \| Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance			1,253	2,944
Impaired Financing Receivable, Related Allowance	178		37
Allowance for Loan and Lease Losses, Write-offs	(63)	(15)
Allowance for Loan and Lease Loss, Recovery of Bad Debts	194	27
Provision for Loan and Lease Losses	(582)	829
Financing Receivable, Individually Evaluated for Impairment	178	387	37
Financing Receivable, Collectively Evaluated for Impairment	624	3,398
Loans and Leases Receivable, Net of Deferred Income	93,675	66,782	101,483
Financing Receivable, Individually Evaluated for Impairment	3,729	3,972
Financing Receivable, Collectively Evaluated for Impairment	$ 89,946	$ 62,810

Loans and Leases Receivable Allowance Covered And Noncovered

No definition available.

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- Definition

Loans and Leases Receivable Net Of Deferred Income Covered And Noncovered

+ References

No definition available.

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- Definition

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (a)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

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-Subparagraph (SX 210.9-03.7(d))

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph d

-Article 9

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- Definition

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

+ References

No definition available.

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- Definition

The balance of financing receivables that were acquired with deteriorated credit quality.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

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- Definition

The valuation allowance for financing receivables acquired with deteriorated credit quality.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953423-111524

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- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Paragraph 11B

-Subparagraph (g)

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- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Paragraph 11B

-Subparagraph (g)

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- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

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The balance of financing receivables that were individually evaluated for impairment.

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- Definition

Amount of allowance for credit losses related to recorded investment.

+ References

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(d))

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-Number 210

-Section 03

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-Subparagraph d

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section L

-Subsection 1

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- Definition

Amount of allowance for loan and lease losses covered by loss sharing agreements.

+ References

No definition available.

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- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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- Definition

Amount of expense related to estimated loss from loan and lease transactions.

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-Publisher FASB

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-Paragraph 1

-Subparagraph (SX 210.9-04.11)

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