Finance Receivables and Allowance for Credit Losses - Schedule of Composition of Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	$ 6,318,201	$ 5,082,964
Allowance for loan losses	(44,297)	(41,741)
Allowance for loan losses - covered loans	(3,552)	(5,404)
Net loans	6,270,352	5,035,819
Commercial Loan Including Finance Lease [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	1,629,600	1,373,415
Commercial Real Estate - Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	134,552	88,630
Commercial Real Estate - Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	1,576,558	1,072,260
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	1,519,156	1,359,569
Consumer Credit - Heloc [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	360,320	251,102
Consumer Credit - Auto [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	846,969	620,473
Consumer Credit - Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	103,338	99,683
Covered Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans by lending classification	$ 147,708	$ 217,832

Amount of allowance for loan and lease losses for loans that are not covered by loss sharing agreements.

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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

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 4

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-Topic 310

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- Definition

Amount after allowance and 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 and loans held for sale.

+ References

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

-Publisher FASB

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-Topic 310

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-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522

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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)

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