TriCo Bancshares Condensed Financial Statements (Parent Only) - Condensed Statements of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities:
Net income	$ 68,320	$ 40,554	$ 44,811
Adjustments to reconcile net income to net cash provided by operating activities:
Equity compensation vesting expense	1,462	1,586	1,467
Net cash from operating activities	91,069	55,381	48,226
Financing activities:
Issuance of common stock through option exercise	218	396	518
Equity compensation tax effect			155
Repurchase of common stock	(2,483)	(1,629)	(1,890)
Cash dividends paid - common	(18,769)	(15,131)	(13,695)
Net cash from financing activities	73,039	201,880	93,316
Net change in cash and cash equivalents	22,105	(100,184)	2,151
Cash and cash equivalents at beginning of year	205,428	305,612	303,461
Cash and cash equivalents at end of year	227,533	205,428	305,612
Parent [Member]
Operating activities:
Net income	68,320	40,554	44,811
Adjustments to reconcile net income to net cash provided by operating activities:
Undistributed equity in earnings of Tri Counties Bank	(45,315)	(23,359)	(29,764)
Equity compensation vesting expense	1,462	1,586	1,467
Equity compensation tax effect			(155)
Net change in other assets and liabilities	(4,983)	(1,295)	(1,210)
Net cash from operating activities	19,484	17,486	15,149
Financing activities:
Issuance of common stock through option exercise	218	396	518
Equity compensation tax effect			155
Repurchase of common stock	(2,483)	(1,629)	(1,890)
Cash dividends paid - common	(18,769)	(15,131)	(13,695)
Net cash from financing activities	(21,034)	(16,364)	(14,912)
Net change in cash and cash equivalents	(1,550)	1,122	237
Cash and cash equivalents at beginning of year	3,924	2,802	2,565
Cash and cash equivalents at end of year	$ 2,374	$ 3,924	$ 2,802