Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Jul. 31, 2020
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2020
Entity File Number	001-34403
Entity Registrant Name	Territorial Bancorp Inc.
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	26-4674701
Entity Address, Address Line One	1132 Bishop Street, Suite 2200
Entity Address, City or Town	Honolulu
Entity Address, State or Province	HI
Entity Address, Postal Zip Code	96813
City Area Code	808
Local Phone Number	946-1400
Title of 12(b) Security	Common stock
Trading Symbol	TBNK
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		9,513,867
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001447051
Amendment Flag	false