TriCo Bancshares Condensed Financial Statements (Parent Only) (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating activities:
Net income	$ 4,722	$ 5,020	$ 5,321	$ 3,931	$ 6,549	$ 6,470	$ 2,771	$ 2,800	$ 18,994	$ 18,590	$ 6,005
Adjustments to reconcile net income to net cash provided by operating activities:
Stock option vesting expense									1,083	830	800
Stock option excess tax benefits									(44)	(296)	(390)
Net cash provided by operating activities									56,486	31,664	51,186
Financing activities:
Stock option excess tax benefits									44	296	390
Repurchase of common stock										(753)	(338)
Cash dividends paid - common									(5,757)	(5,742)	(6,344)
Net cash used for financing activities									30,315	81,184	(87,162)
Increase in cash and cash equivalents									111,624	266,209	24,477
Cash and cash equivalents and beginning of year				637,275				371,066	637,275	371,066	346,589
Cash and cash equivalents at end of year	748,899				637,275				748,899	637,275	371,066
Parent [Member]
Operating activities:
Net income									18,994	18,590	6,005
Adjustments to reconcile net income to net cash provided by operating activities:
Over (under) distributed equity in earnings of Tri Counties Bank									(11,632)	(12,470)	534
Stock option vesting expense									1,083	830	800
Stock option excess tax benefits									(44)	(296)	(390)
Net change in other assets and liabilities									(1,089)	(818)	(802)
Net cash provided by operating activities									7,312	5,836	6,147
Financing activities:
Issuance of common stock through option exercise									206	436	203
Stock option excess tax benefits									44	296	390
Repurchase of common stock										(753)	(338)
Cash dividends paid - common									(5,757)	(5,742)	(6,344)
Net cash used for financing activities									(5,507)	(5,763)	(6,089)
Increase in cash and cash equivalents									1,805	73	58
Cash and cash equivalents and beginning of year				706				633	706	633	575
Cash and cash equivalents at end of year	$ 2,511				$ 706				$ 2,511	$ 706	$ 633