Changes in Allowance for Loan Losses by Loan Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Allowance for loan losses:
Beginning balance	$ 69,366	$ 70,898
Provision for losses	2,102	4,875
Recoveries on loans	3,746	898
Loans charged off	(6,677)	(6,302)
Ending balance	68,537	70,369
Commercial
Allowance for loan losses:
Beginning balance	25,913	17,731
Provision for losses	358	577
Recoveries on loans	1,873	148
Loans charged off	(2,773)	(2,882)
Ending balance	25,371	15,574
Commercial Real Estate
Allowance for loan losses:
Beginning balance	26,703	37,919
Provision for losses	(755)	1,778
Recoveries on loans	1,376	228
Loans charged off	(2,346)	(2,018)
Ending balance	24,978	37,907
Consumer
Allowance for loan losses:
Beginning balance	2,593	2,902
Provision for losses	73	16
Recoveries on loans	209	208
Loans charged off	(186)	(321)
Ending balance	2,689	2,805
Residential
Allowance for loan losses:
Beginning balance	14,157	12,343
Provision for losses	2,406	2,508
Recoveries on loans	288	313
Loans charged off	(1,372)	(1,081)
Ending balance	15,479	14,083
Finance Lease
Allowance for loan losses:
Beginning balance		3
Provision for losses	20	(4)
Recoveries on loans		1
Ending balance	$ 20	$ 0

Reflects the amount of loans and leases that have been removed, or charged off, from both loan receivables and the reserve for credit losses, typically because they are considered to be not salvageable or have been purchased by unconsolidated collection entities.

+ References+ Details

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 Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 8, 9

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (b)(1)(ii)

-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

Reference 3: 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))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Section 563c.102

-Paragraph 8

-Subparagraph a(ii)

-Chapter V

-Subsection I

-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph d

-Article 9

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 114

-Paragraph 20

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section L

-Subsection 1

+ Details

- Definition

The sum of the periodic provision charged to earnings, based on an assessment of uncollectibility from the counterparty on account of loan, lease or other credit losses, to reduce these accounts to the amount that approximates their net realizable value.

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