TriCo Bancshares Condensed Financial Statements (Parent Only) (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012
Operating activities:
Net income	$ 8,477	$ 4,722	$ 5,020	$ 5,321	$ 3,931
Adjustments to reconcile net income to net cash provided by operating activities:
Stock option vesting expense	236				257
Stock option excess tax benefits	(20)
Net cash provided by operating activities	13,285				17,953
Financing activities:
Stock option excess tax benefits	20
Cash dividends paid - common	(1,441)				(1,438)
Net cash used for financing activities	(6,645)				(25,695)
Net change in cash and cash equivalents	53,372				44,485
Cash and cash equivalents at beginning of period	748,899			681,760	637,275
Cash and cash equivalents at end of period	802,271	748,899			681,760
Parent [Member]
Operating activities:
Net income	8,477				3,931
Adjustments to reconcile net income to net cash provided by operating activities:
Under distributed equity in earnings of Tri Counties Bank	(7,041)				(2,583)
Stock option vesting expense	236				257
Stock option excess tax benefits	(20)
Net change in other assets and liabilities	(245)				(246)
Net cash provided by operating activities	1,407				1,359
Financing activities:
Stock option excess tax benefits	20
Cash dividends paid - common	(1,441)				(1,438)
Net cash used for financing activities	(1,421)				(1,438)
Net change in cash and cash equivalents	(14)				(79)
Cash and cash equivalents at beginning of period	2,511				706
Cash and cash equivalents at end of period	$ 2,497				$ 627