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Nature of Banking Activities and Significant Accounting policies - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2016 USD ($) Entity | Dec. 31, 2015 USD ($)
Nature Of Banking Activities And Significant Accounting Policies [Line Items] |  |
Number of accounts included by parent company | Entity | 6 |
Recognition of other than temporary impairment on basis of credit loss description | If there is no credit loss, there is no other-than-temporary impairment. If there is a credit loss, other-than-temporary impairment exists, and the credit loss must be recognized in net income and the remaining portion of impairment must be recognized in other comprehensive income (loss). |
Gain (loss) on rate lock commitments | $ 0 |
Accrual status of loan | 90 days |
Troubled debt restructurings (TDRs), amount | $ 460,000 | $ 982,000
Bank-owned life insurance, death benefits received | $ 425,000 | 373,000
Largest amount of tax benefit realized by taxing authority | 50.00% |
Liability for unrecognized tax benefits | $ 0 | 0
Advertising cost | 402,000 | 400,000
Life Insurance Product Line [Member] |  |
Nature Of Banking Activities And Significant Accounting Policies [Line Items] |  |
Bank-owned life insurance, death benefits received | $ 102,000 | $ 0
Minimum [Member] |  |
Nature Of Banking Activities And Significant Accounting Policies [Line Items] |  |
Period of time between issuance of a loan commitment and closing and sale of the loan | 30 days |
Company not considered value of impairment on individual consumer, residential and small commercial loans | $ 250,000 |
Management's policy on evaluation of impairment | $ 250,000 |
Minimum [Member] | Software [Member] |  |
Nature Of Banking Activities And Significant Accounting Policies [Line Items] |  |
Estimated useful lives of depreciation of premises and equipment | 3 years |
Minimum [Member] | Core Deposits [Member] |  |
Nature Of Banking Activities And Significant Accounting Policies [Line Items] |  |
Intangible assets, estimated useful lives | 6 years |
Minimum [Member] | Premises and Equipment [Member] |  |
Nature Of Banking Activities And Significant Accounting Policies [Line Items] |  |
Estimated useful lives of depreciation of premises and equipment | 3 years |
Maximum [Member] |  |
Nature Of Banking Activities And Significant Accounting Policies [Line Items] |  |
Period of time between issuance of a loan commitment and closing and sale of the loan | 60 days |
Maximum [Member] | Software [Member] |  |
Nature Of Banking Activities And Significant Accounting Policies [Line Items] |  |
Estimated useful lives of depreciation of premises and equipment | 7 years |
Maximum [Member] | Core Deposits [Member] |  |
Nature Of Banking Activities And Significant Accounting Policies [Line Items] |  |
Intangible assets, estimated useful lives | 9 years |
Maximum [Member] | Premises and Equipment [Member] |  |
Nature Of Banking Activities And Significant Accounting Policies [Line Items] |  |
Estimated useful lives of depreciation of premises and equipment | 40 years |

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