TriCo Bancshares Condensed Financial Statements (Parent Only) - Statements of Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended							9 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating activities:
Net income	$ 11,897	$ 13,589	$ 12,079	$ 12,533	$ 12,199	$ 9,405	$ 10,674	$ 37,565	$ 32,278
Adjustments to reconcile net income to net cash provided by operating activities:
Equity compensation vesting expense								1,184	1,078
Net cash from operating activities								45,817	38,884
Financing activities:
Equity compensation net (excess tax benefit) tax expense									(182)
Repurchase of common stock								(1,629)	(384)
Cash dividends paid - common								(11,228)	(10,265)
Net cash provided by financing activities								100,469	40,109
Net change in cash and cash equivalents								(117,578)	11,627
Cash and cash equivalents and beginning of year			305,612	315,088			303,461	305,612	303,461
Cash and cash equivalents at end of period	188,034			305,612	315,088			188,034	315,088
Parent [Member]
Operating activities:
Net income	11,897				12,199			37,565	32,278
Adjustments to reconcile net income to net cash provided by operating activities:
Over (under) distributed equity in earnings of Tri Counties Bank	(7,211)				(8,522)			(24,594)	(22,116)
Equity compensation vesting expense								1,184	1,078
Equity compensation net (excess tax benefit) tax expense									182
Net change in other assets and liabilities								(1,015)	(906)
Net cash from operating activities								13,140	10,516
Financing activities:
Issuance of common stock through option exercise								193	518
Equity compensation net (excess tax benefit) tax expense									(182)
Repurchase of common stock								(1,629)	(384)
Cash dividends paid - common								(11,228)	(10,265)
Net cash provided by financing activities								(12,664)	(10,313)
Net change in cash and cash equivalents								476	203
Cash and cash equivalents and beginning of year			$ 2,802	2,768			$ 2,565	2,802	2,565
Cash and cash equivalents at end of period	$ 3,278			$ 2,802	$ 2,768			$ 3,278	$ 2,768