International Activities - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
International Activities [Line Items]
Revenues from international trust-related services	$ 26,000	$ 31,000	$ 26,000
Loans to foreign borrowers	265,000	213,000
Deposits at Cayman Islands office	$ 170,170	$ 176,582
Geographic Concentration Risk [Member] \| Assets, Total [Member]
International Activities [Line Items]
Concentration risk percentage	1.00%
Geographic Concentration Risk [Member] \| Sales Revenue, Net [Member]
International Activities [Line Items]
Concentration risk percentage	1.00%

International Activities [Line Items]

No definition available.

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- Definition

Amount of revenues related to trust related services, including wealth management services, offered internationally.

+ References

No definition available.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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- Definition

The aggregate of all foreign interest-bearing and noninterest-bearing deposit liabilities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(a))
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- Definition

Amount after allowance and deduction of deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts, of loans and leases to borrowers not within the country of domicile of the reporting entity. 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
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