Parent Company Only - Condensed Statements of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Interest and dividend income:
Total interest income	$ 69,088	$ 62,702
Noninterest expense:
Salaries	20,832	22,259
Other general and administrative expenses	4,388	4,252
Total noninterest expense	38,268	38,798
Income before income taxes	6,837	21,474
Income taxes	1,810	5,318
Net income	5,027	16,156
Territorial Bancorp Inc.
Interest and dividend income:
Dividends from Territorial Savings Bank		17,500
Total interest income	4	17,504
Noninterest expense:
Salaries	42	42
Other general and administrative expenses	958	656
Total noninterest expense	1,000	698
Income before income taxes	(996)	16,806
Income taxes	(315)	(209)
Income before equity in undistributed earnings in subsidiaries	(681)	17,015
Equity in undistributed earnings of Territorial Savings Bank, net of dividends	5,708	(859)
Net income	5,027	16,156
Territorial Bancorp Inc. | Territorial Savings Bank
Interest and dividend income:
Interest-earning deposit with Territorial Savings Bank	$ 4	$ 4