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Employee Benefit Plans (Details) | 12 Months Ended
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Dec. 31, 2015 USD ($) installment $ / shares shares | Dec. 31, 2014 USD ($) $ / shares shares | Dec. 31, 2013 USD ($) $ / shares shares | Dec. 31, 2008 shares
Defined Benefit Plan Disclosure |  |  |  |
Employer contribution for defined contribution plan | $ | $ 1,000,000 | $ 900,000 | $ 700,000 |
Employee Stock Ownership Plan, common stock, shares outstanding (shares) | shares | 155,309 |  |  |
Employee Stock Ownership Plan, common stock, fair value | $ | $ 14,100,000 |  |  |
Employee Stock Ownership Plan ESOP Plan |  |  |  |
Defined Benefit Plan Disclosure |  |  |  |
Employee Stock Ownership Plan, service period eligible to participate (years) | 1 year |  |  |
Participants vesting percentage after three years of continuous service (percent) | 100.00% |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period | 3 years |  |  |
Initial Public Offering |  |  |  |
Defined Benefit Plan Disclosure |  |  |  |
Contribution to Employee Stock Ownership Plan, common stock (shares) | shares |  |  |  | 22,500
Outside Directors |  |  |  |
Defined Benefit Plan Disclosure |  |  |  |
Number of deferred common stock (shares) | shares | 8,466 | 9,415 | 7,173 |
Weighted-average grant date fair values of deferred common stock (dollars per share) | $ / shares | $ 78.62 | $ 70.63 | $ 66.77 |
Nonqualified Deferred Compensation Plan |  |  |  |
Defined Benefit Plan Disclosure |  |  |  |
Deferred compensation expense | $ | $ 106,000 | $ 82,000 | $ 46,000 |
Number of annual installments of deferred compensation (installment) | installment | 2 |  |  |
Number of days after departure from board of directors for payment of deferred compensation (days) | 90 days |  |  |

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- Definition The compensation expense recognized during the period pertaining to the deferred compensation arrangement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 710 -SubTopic 10 -Section 30 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363 + Details
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- Definition The fair value of shares held by the ESOP as of the balance sheet date in which no ESOP participant has a vested interest and no lender has a claim. The fair value of an ESOP share is the amount the seller could reasonably expect to receive for it in a current sale between a willing buyer and a willing seller, that is, other than in a forced or liquidation sale, which would be the market price of the stock if it is publicly traded. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 40 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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