Deposits - Components of interest expense recognized on interest-bearing deposits (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Interest expense recognized on interest-bearing deposits
Savings	$ 32us-gaap_InterestExpenseSavingsDeposits	$ 40us-gaap_InterestExpenseSavingsDeposits	$ 32us-gaap_InterestExpenseSavingsDeposits
Money market	174	229	392
NOW accounts	209	251	270
Time certificates of deposit	645	750	936
Total interest expense recognized	$ 1,060	$ 1,270	$ 1,630

Aggregate amount of all interest expense on domestic deposit liabilities.

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

+ Details

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

- Definition

Amount of interest expense on domestic certificates of deposit liabilities.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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- Details

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Period Type:	duration

- Definition

Interest expense incurred on all money market deposits.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Interest expense incurred on the amount of Negotiable Order of Withdrawal (NOW). Interest-bearing transaction account that combines the payable on demand feature of checks and investment feature of savings accounts. A NOW account is functionally an interest paying checking account.

+ References

+ Details

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- Definition

Interest expense incurred on all savings account deposits.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration