{"cik":1464963,"taxonomy":"us-gaap","tag":"EarningsPerShareBasic","label":"Earnings Per Share, Basic","description":"The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.","entityName":"FIRST EAGLE ALTERNATIVE CAPITAL BDC, INC.","units":{"USD/shares":[{"start":"2021-01-01","end":"2021-09-30","val":0.65,"accn":"0000950170-22-023332","fy":2022,"fp":"Q3","form":"10-Q","filed":"2022-11-08"},{"start":"2021-07-01","end":"2021-09-30","val":0.09,"accn":"0000950170-22-023332","fy":2022,"fp":"Q3","form":"10-Q","filed":"2022-11-08","frame":"CY2021Q3"},{"start":"2022-01-01","end":"2022-09-30","val":-0.89,"accn":"0000950170-22-023332","fy":2022,"fp":"Q3","form":"10-Q","filed":"2022-11-08"},{"start":"2022-07-01","end":"2022-09-30","val":-0.04,"accn":"0000950170-22-023332","fy":2022,"fp":"Q3","form":"10-Q","filed":"2022-11-08","frame":"CY2022Q3"}]}}