TriCo Bancshares Condensed Financial Statements (Parent Only) - Condensed Statements of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating activities:
Net income	$ 64,814	$ 92,072	$ 68,320
Adjustments to reconcile net income to net cash provided by operating activities:
Equity compensation vesting expense	2,036	1,654	1,462
Net cash from operating activities	114,802	102,806	91,069
Financing activities:
Issuance of common stock through option exercise	198	9	218
Repurchase of common stock, net	(26,720)	(2,196)	(2,483)
Cash dividends paid — common	(26,303)	(24,999)	(18,769)
Net cash from financing activities	1,094,575	(24,043)	73,039
Net change in cash and cash equivalents	393,044	48,974	22,105
Cash and cash equivalents at beginning of year	276,507	227,533	205,428
Cash and cash equivalents at end of year	669,551	276,507	227,533
Parent
Operating activities:
Net income	64,814	92,072	68,320
Adjustments to reconcile net income to net cash provided by operating activities:
Undistributed equity in earnings of Tri Counties Bank	(3,851)	(62,326)	(45,315)
Equity compensation vesting expense	2,036	1,654	1,462
Net change in other assets and liabilities	(1,885)	(1,580)	(4,983)
Net cash from operating activities	61,114	29,820	19,484
Financing activities:
Issuance of common stock through option exercise	198	9	218
Repurchase of common stock, net	(26,720)	(2,196)	(2,483)
Cash dividends paid — common	(26,303)	(24,999)	(18,769)
Net cash from financing activities	(52,825)	(27,186)	(21,034)
Net change in cash and cash equivalents	8,289	2,634	(1,550)
Cash and cash equivalents at beginning of year	5,008	2,374	3,924
Cash and cash equivalents at end of year	$ 13,297	$ 5,008	$ 2,374