Organization and Summary of Significant Accounting Policies	6 Months Ended
Jun. 30, 2017
Organization and Summary of Significant Accounting Policies [Abstract]
Organization and Summary of Significant Accounting Policies	1. Organization and Summary of Significant Accounting Policies (a) The Company and Basis of Presentation AeroCentury Corp., a Delaware corporation incorporated in 1997, typically acquires used regional aircraft and engines for lease to foreign and domestic regional carriers. In August 2016, AeroCentury Corp. formed two wholly-owned subsidiaries, ACY 19002 Limited ("ACY 19002") and ACY 19003 Limited ("ACY 19003") for the purpose of acquiring aircraft using a combination of cash and financing ("SPE Financing") separate from the parent's credit facility. Financial information for AeroCentury Corp., ACY 19002 and ACY 19003 (collectively, the "Company") is presented on a consolidated basis in accordance with accounting principles generally accepted in the United States of America ("GAAP") for interim financial information, the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three-month period ended June 30, 2017 are not necessarily indicative of the results that may be expected for the year ending December 31, 2017. All intercompany balances and transactions have been eliminated in consolidation. For further information, refer to the financial statements and footnotes thereto included in the Company's annual report on Form 10-K for the year ended December 31, 2016. (b) Use of Estimates The Company's condensed consolidated financial statements have been prepared in accordance with GAAP. The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable for making judgments that are not readily apparent from other sources. The most significant estimates with regard to these condensed consolidated financial statements are the residual values and useful lives of the Company's long lived assets, the amount and timing of future cash flows associated with each asset that are used to evaluate whether assets are impaired, accrued maintenance costs, accounting for income taxes, and the amounts recorded as allowances for doubtful accounts. (c) Fair Value Measurements Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs, to the extent possible. The fair value hierarchy under GAAP is based on three levels of inputs. Level 1 - Quoted prices in active markets for identical assets or liabilities. Level 2 - Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 - Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Assets and Liabilities Measured and Recorded at Fair Value on a Recurring Basis The carrying amount of the Company's money market funds included in cash and cash equivalents was $2,848,700 and $1,348,100 at June 30, 2017 and December 31, 2016, respectively. The fair value of the Company's money market funds is categorized as Level 1 under the GAAP fair value hierarchy. As of June 30, 2017 and December 31, 2016, there were no liabilities that were required to be measured and recorded at fair value on a recurring basis. Assets Measured and Recorded at Fair Value on a Nonrecurring Basis The Company determines fair value of long-lived assets held and used, such as aircraft and aircraft engines held for lease and assets held for sale, by reference to independent appraisals, quoted market prices (e.g., offers to purchase) and other factors. An impairment charge is recorded when the Company believes that the carrying value of an asset will not be recovered through future net cash flows and that the asset's carrying value exceeds its fair value. Assets held for lease The Company recorded an impairment charge of $454,300 on one of its assets held for lease in the quarter ended June 30, 2017. Assets held for sale The Company recorded no impairment charges on its aircraft held for sale during the three months or six months ended June 30, 2017. During the three months and six months ended June 30, 2016, the Company recorded impairment charges of $246,200 and $321,200, respectively, on assets prior to their sale during 2016. Fair Value of Other Financial Instruments The Company's financial instruments, other than cash and cash equivalents, consist principally of finance leases receivable, amounts borrowed under its credit facility (the "Credit Facility") and notes payable under special purpose financing. The fair value of accounts receivable, finance leases receivable, accounts payable and the Company's maintenance reserves and accrued maintenance costs approximates the carrying value of these financial instruments. Borrowings under the Company's Credit Facility bear floating rates of interest that reset periodically to a market benchmark rate plus a credit margin. The Company believes that the effective interest rate under the Credit Facility approximates current market rates for such indebtedness at the balance sheet date, and therefore that the outstanding principal and accrued interest of $133,453,200 and $110,183,600 at June 30, 2017 and December 31, 2016, respectively, approximate their fair values on such dates. The fair value of the Company's outstanding balance of its Credit Facility would be categorized as Level 3 under the GAAP fair value hierarchy. The amounts payable under the Company's SPE Financing are payable through the fourth quarter of 2020 and bear a fixed rate of interest, as described in Note 4(b) to the condensed consolidated financial statements. The Company believes that the effective interest rate under the SPE Financing approximates current market rates for such indebtedness at the balance sheet date, and therefore that the outstanding principal and accrued interest of $15,614,700 and $17,654,200 approximates the fair value of such notes at June 30, 2017 and December 31, 2016, respectively. Such fair value would be categorized as Level 3 under the GAAP fair value hierarchy. (d) Finance Leases As of June 30, 2017, the Company had six aircraft subject to sales-type finance leases and three aircraft subject to direct financing leases. All such leases contain lessee bargain purchase options at prices substantially below the assets' estimated residual values at the exercise date for the options. Consequently, the Company has classified each of these leases as finance leases for financial accounting purposes. For such finance leases, the Company reports the discounted present value of (i) future minimum lease payments (including the bargain purchase option) and (ii) any residual value not subject to a bargain purchase option as a finance lease receivable on its balance sheet and accrues interest on the balance of the finance lease receivable based on the interest rate inherent in the applicable lease over the term of the lease. For sales-type finance leases, the Company recognizes as a gain or loss the amount equal to (i) the net investment in sales-type finance leases plus any initial direct costs and lease incentives less (ii) the net book value of the aircraft. The Company recognized interest earned on finance leases in the amount of $432,300 and $187,000 in the quarters ended June 30, 2017 and 2016, respectively and $757,700 and $372,100 in the six month periods ended June 30, 2017 and 2016, respectively. (e) Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-09 that created the new Topic 606 ("Topic 606") in the Accounting Standards Codification ("ASC"). Topic 606 also included numerous conforming additions and amendments to other Topics within the ASC. Topic 606 established new rules that affect the amount and timing of revenue recognition for contracts with customers, but does not affect lease accounting and reporting. As such, adoption of these provisions will not affect the Company's lease revenues but may affect the reporting of other of the Company's revenues. On August 12, 2015, the FASB deferred the effective date of the provisions included in Topic 606 to years commencing after December 15, 2017. Topic 606 can be adopted early for years commencing after December 15, 2016, and may be reflected using either a full retrospective method or a simplified method that does not recast prior periods but does disclose the effect of the adoption on the current period consolidated financial statements. The Company has not yet determined either the potential impact on its consolidated financial statements or the method it will elect to use in connection with the adoption of the changes included in Topic 606. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) ("ASU 2016-02"). ASU 2016-02 is effective for public companies for years beginning after December 15, 2018, although early adoption is permitted. ASU 2016-02 substantially modifies lessee accounting for leases, requiring that lessees recognize lease assets and liabilities for leases extending beyond one year. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. The new standard requires a lessor to classify leases as sales-type, finance or operating. A lease will be treated as a sale if it transfers all of the risks and rewards, as well as control of the underlying asset, to the lessee. If risks and rewards are conveyed without the transfer of control, the lease is treated as a financing. If the lessor does not convey risks and rewards or control, an operating lease results. A modified retrospective transition approach is required for lessors for sales-type, finance, and operating leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements, with certain practical expedients available. The Company is reviewing those agreements under which it is the lessor and is evaluating the impact of the adoption of ASU 2016-02 on its consolidated financial statements and related disclosures. The Company does not expect to adopt ASU 2016-02 early, and does expect to elect practical expedients in connection with its adoption, including not re-evaluating lease classification or capitalized initial direct costs on existing leases. The Company is not an obligor under any agreements that would be considered leases under ASU 2016-02, and so would be unaffected with respect to its adoption with respect to lessee accounting. In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805) ("ASU 2017-01"). ASU 2017-01 is effective for public companies for years beginning after December 15, 2017, although early adoption is permitted. ASU 2017-01 clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The Company has early adopted ASU 2017-01 effective beginning the first quarter ended March 31, 2017 and has determined that none of its acquired assets qualifies as a business, such that no gain, loss or adjustment to the carrying value of assets was required in connection with such adoption. In January 2017, the FASB issued ASU 2017-04, Intangibles -- Goodwill and Other (Topic 350) ("ASU 2017-04"), which provides for simplification of the test for goodwill impairment. Under the revised standard, "step 2" of the test under the previous standard is eliminated and (i) the fair value of the reporting unit is compared to its carrying value, with (ii) an impairment charge up to the amount of goodwill recognized for the excess of carrying value over fair value (considering the income tax effects of deductible goodwill, if applicable). The new provisions are required to be adopted for fiscal years beginning after December 15, 2019, although the Company has elected to early adopt the new provisions beginning with its quarter ended March 31, 2017. Adoption of ASU 2017-04 had no effect on the financial results or position of the Company.

1. Organization and Summary of Significant Accounting Policies

(a) The Company and Basis of Presentation

AeroCentury Corp., a Delaware corporation incorporated in 1997, typically acquires used regional aircraft and engines for lease to foreign and domestic regional carriers.

In August 2016, AeroCentury Corp. formed two wholly-owned subsidiaries, ACY 19002 Limited ("ACY 19002") and ACY 19003 Limited ("ACY 19003") for the purpose of acquiring aircraft using a combination of cash and financing ("SPE Financing") separate from the parent's credit facility. Financial information for AeroCentury Corp., ACY 19002 and ACY 19003 (collectively, the "Company") is presented on a consolidated basis in accordance with accounting principles generally accepted in the United States of America ("GAAP") for interim financial information, the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three-month period ended June 30, 2017 are not necessarily indicative of the results that may be expected for the year ending December 31, 2017. All intercompany balances and transactions have been eliminated in consolidation.

For further information, refer to the financial statements and footnotes thereto included in the Company's annual report on Form 10-K for the year ended December 31, 2016.

(b) Use of Estimates

The Company's condensed consolidated financial statements have been prepared in accordance with GAAP. The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable for making judgments that are not readily apparent from other sources.

The most significant estimates with regard to these condensed consolidated financial statements are the residual values and useful lives of the Company's long lived assets, the amount and timing of future cash flows associated with each asset that are used to evaluate whether assets are impaired, accrued maintenance costs, accounting for income taxes, and the amounts recorded as allowances for doubtful accounts.

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs, to the extent possible. The fair value hierarchy under GAAP is based on three levels of inputs.

Level 1 - Quoted prices in active markets for identical assets or liabilities.

Level 2 - Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3 - Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

Assets and Liabilities Measured and Recorded at Fair Value on a Recurring Basis

The carrying amount of the Company's money market funds included in cash and cash equivalents was $2,848,700 and $1,348,100 at June 30, 2017 and December 31, 2016, respectively. The fair value of the Company's money market funds is categorized as Level 1 under the GAAP fair value hierarchy.

As of June 30, 2017 and December 31, 2016, there were no liabilities that were required to be measured and recorded at fair value on a recurring basis.

Assets Measured and Recorded at Fair Value on a Nonrecurring Basis

The Company determines fair value of long-lived assets held and used, such as aircraft and aircraft engines held for lease and assets held for sale, by reference to independent appraisals, quoted market prices (e.g., offers to purchase) and other factors. An impairment charge is recorded when the Company believes that the carrying value of an asset will not be recovered through future net cash flows and that the asset's carrying value exceeds its fair value.

Assets held for lease

The Company recorded an impairment charge of $454,300 on one of its assets held for lease in the quarter ended June 30, 2017.

Assets held for sale

The Company recorded no impairment charges on its aircraft held for sale during the three months or six months ended June 30, 2017. During the three months and six months ended June 30, 2016, the Company recorded impairment charges of $246,200 and $321,200, respectively, on assets prior to their sale during 2016.

Fair Value of Other Financial Instruments

The Company's financial instruments, other than cash and cash equivalents, consist principally of finance leases receivable, amounts borrowed under its credit facility (the "Credit Facility") and notes payable under special purpose financing. The fair value of accounts receivable, finance leases receivable, accounts payable and the Company's maintenance reserves and accrued maintenance costs approximates the carrying value of these financial instruments.

Borrowings under the Company's Credit Facility bear floating rates of interest that reset periodically to a market benchmark rate plus a credit margin. The Company believes that the effective interest rate under the Credit Facility approximates current market rates for such indebtedness at the balance sheet date, and therefore that the outstanding principal and accrued interest of $133,453,200 and $110,183,600 at June 30, 2017 and December 31, 2016, respectively, approximate their fair values on such dates. The fair value of the Company's outstanding balance of its Credit Facility would be categorized as Level 3 under the GAAP fair value hierarchy.

The amounts payable under the Company's SPE Financing are payable through the fourth quarter of 2020 and bear a fixed rate of interest, as described in Note 4(b) to the condensed consolidated financial statements. The Company believes that the effective interest rate under the SPE Financing approximates current market rates for such indebtedness at the balance sheet date, and therefore that the outstanding principal and accrued interest of $15,614,700 and $17,654,200 approximates the fair value of such notes at June 30, 2017 and December 31, 2016, respectively. Such fair value would be categorized as Level 3 under the GAAP fair value hierarchy.

(d) Finance Leases

As of June 30, 2017, the Company had six aircraft subject to sales-type finance leases and three aircraft subject to direct financing leases. All such leases contain lessee bargain purchase options at prices substantially below the assets' estimated residual values at the exercise date for the options. Consequently, the Company has classified each of these leases as finance leases for financial accounting purposes. For such finance leases, the Company reports the discounted present value of (i) future minimum lease payments (including the bargain purchase option) and (ii) any residual value not subject to a bargain purchase option as a finance lease receivable on its balance sheet and accrues interest on the balance of the finance lease receivable based on the interest rate inherent in the applicable lease over the term of the lease. For sales-type finance leases, the Company recognizes as a gain or loss the amount equal to (i) the net investment in sales-type finance leases plus any initial direct costs and lease incentives less (ii) the net book value of the aircraft.

The Company recognized interest earned on finance leases in the amount of $432,300 and $187,000 in the quarters ended June 30, 2017 and 2016, respectively and $757,700 and $372,100 in the six month periods ended June 30, 2017 and 2016, respectively.

(e) Recent Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-09 that created the new Topic 606 ("Topic 606") in the Accounting Standards Codification ("ASC"). Topic 606 also included numerous conforming additions and amendments to other Topics within the ASC. Topic 606 established new rules that affect the amount and timing of revenue recognition for contracts with customers, but does not affect lease accounting and reporting. As such, adoption of these provisions will not affect the Company's lease revenues but may affect the reporting of other of the Company's revenues. On August 12, 2015, the FASB deferred the effective date of the provisions included in Topic 606 to years commencing after December 15, 2017. Topic 606 can be adopted early for years commencing after December 15, 2016, and may be reflected using either a full retrospective method or a simplified method that does not recast prior periods but does disclose the effect of the adoption on the current period consolidated financial statements. The Company has not yet determined either the potential impact on its consolidated financial statements or the method it will elect to use in connection with the adoption of the changes included in Topic 606.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) ("ASU 2016-02"). ASU 2016-02 is effective for public companies for years beginning after December 15, 2018, although early adoption is permitted. ASU 2016-02 substantially modifies lessee accounting for leases, requiring that lessees recognize lease assets and liabilities for leases extending beyond one year. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement.

The new standard requires a lessor to classify leases as sales-type, finance or operating. A lease will be treated as a sale if it transfers all of the risks and rewards, as well as control of the underlying asset, to the lessee. If risks and rewards are conveyed without the transfer of control, the lease is treated as a financing. If the lessor does not convey risks and rewards or control, an operating lease results. A modified retrospective transition approach is required for lessors for sales-type, finance, and operating leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements, with certain practical expedients available.

The Company is reviewing those agreements under which it is the lessor and is evaluating the impact of the adoption of ASU 2016-02 on its consolidated financial statements and related disclosures. The Company does not expect to adopt ASU 2016-02 early, and does expect to elect practical expedients in connection with its adoption, including not re-evaluating lease classification or capitalized initial direct costs on existing leases.

The Company is not an obligor under any agreements that would be considered leases under ASU 2016-02, and so would be unaffected with respect to its adoption with respect to lessee accounting.

In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805) ("ASU 2017-01"). ASU 2017-01 is effective for public companies for years beginning after December 15, 2017, although early adoption is permitted. ASU 2017-01 clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The Company has early adopted ASU 2017-01 effective beginning the first quarter ended March 31, 2017 and has determined that none of its acquired assets qualifies as a business, such that no gain, loss or adjustment to the carrying value of assets was required in connection with such adoption.

In January 2017, the FASB issued ASU 2017-04, Intangibles -- Goodwill and Other (Topic 350) ("ASU 2017-04"), which provides for simplification of the test for goodwill impairment. Under the revised standard, "step 2" of the test under the previous standard is eliminated and (i) the fair value of the reporting unit is compared to its carrying value, with (ii) an impairment charge up to the amount of goodwill recognized for the excess of carrying value over fair value (considering the income tax effects of deductible goodwill, if applicable). The new provisions are required to be adopted for fiscal years beginning after December 15, 2019, although the Company has elected to early adopt the new provisions beginning with its quarter ended March 31, 2017. Adoption of ASU 2017-04 had no effect on the financial results or position of the Company.