Cover - USD ($)	12 Months Ended
	Dec. 31, 2019	Mar. 01, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Entity File Number	0-26589
Entity Registrant Name	FIRST BANCORP, INC
Entity Incorporation, State or Country Code	ME
Entity Tax Identification Number	01-0404322
Entity Address, Address Line One	223 Main Street
Entity Address, City or Town	Damariscotta
Entity Address, State or Province	ME
Entity Address, Postal Zip Code	04543
Entity Central Index Key	0000765207
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 273,082,000
Entity Common Stock, Shares Outstanding		10,920,770
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Shell Company	false
City Area Code	207
Local Phone Number	563-3195
Document Transition Report	false