TriCo Bancshares Condensed Financial Statements (Parent Only) - Condensed Statements of Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Net income	$ 23,657	$ 17,606	$ 7,430	$ 16,121	$ 22,890	$ 23,395	$ 23,061	$ 22,726	$ 64,814	$ 92,072	$ 68,320
Other comprehensive income (loss), net of tax:
Increase (decrease) in unrealized gains on available for sale securities arising during the period									11,126	17,159	(12,434)
Change in minimum pension liability									6,972	(4,502)	388
Change in joint beneficiary agreement liability									(596)	0	426
Other comprehensive income (loss)									17,502	12,657	(11,620)
Comprehensive income									82,316	104,729	56,700
Parent
Condensed Financial Statements, Captions [Line Items]
Net income									64,814	92,072	68,320
Other comprehensive income (loss), net of tax:
Increase (decrease) in unrealized gains on available for sale securities arising during the period									11,126	17,159	(12,434)
Change in minimum pension liability									6,972	(4,502)	388
Change in joint beneficiary agreement liability									(596)	0	426
Other comprehensive income (loss)									17,502	12,657	(11,620)
Comprehensive income									$ 82,316	$ 104,729	$ 56,700