Deposits - Interest Expense on Deposits (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Banking and Thrift [Abstract]
Savings deposits	$ 671us-gaap_InterestExpenseSavingsDeposits	$ 844us-gaap_InterestExpenseSavingsDeposits	$ 900us-gaap_InterestExpenseSavingsDeposits
Time deposits	4,818us-gaap_InterestExpenseTimeDeposits	6,277us-gaap_InterestExpenseTimeDeposits	7,875us-gaap_InterestExpenseTimeDeposits
Interest-bearing demand deposits	2,869	4,228	4,778
Total	$ 8,358us-gaap_InterestExpenseDeposits	$ 11,349us-gaap_InterestExpenseDeposits	$ 13,553us-gaap_InterestExpenseDeposits

The aggregate interest expense incurred on time deposits, including certificates of deposits, in domestic offices.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.6)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 6

-Article 9

Name:	us-gaap_InterestExpenseTimeDeposits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration