TriCo Bancshares Condensed Financial Statements (Parent Only) - Condensed Statements of Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Net income	$ 13,910	$ 2,989	$ 11,897	$ 13,589	$ 12,079
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) on available for sale securities arising during the period	(11,026)				457
Change in minimum pension liability	80				54
Other comprehensive income (loss)	(10,946)				511
Comprehensive income	2,964				12,590
Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	13,910				12,079
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) on available for sale securities arising during the period	(11,026)				457
Change in minimum pension liability	80				54
Other comprehensive income (loss)	(10,946)				511
Comprehensive income	$ 2,964				$ 12,590