TriCo Bancshares Parent Only Financial Statements (Unaudited) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Assets
Cash and Cash equivalents	$ 644,102	$ 637,275	$ 391,054	$ 371,066
Other assets	38,030	43,384
Total assets	2,525,618	2,555,597	2,176,184
Liabilities and shareholders' equity
Other liabilities	30,538	30,427
Junior subordinated debt	41,238	41,238	41,238
Total liabilities	2,302,389	2,339,156
Shareholders' equity:
Common stock, no par value: 50,000,000 shares authorized; issued and outstanding: 15,992,893 at June 30, 2012 15,978,958 at December 31, 2011	84,799	84,079
Retained earnings	134,893	128,551
Accumulated other comprehensive loss, net	3,537	3,811
Total shareholders' equity	223,229	216,441	204,915	200,397
Total liabilities and shareholders' equity	2,525,618	2,555,597
Parent [Member]
Assets
Cash and Cash equivalents	2,733	706	936	633
Investment in Tri Counties Bank	260,774	256,010
Other assets	1,238	1,238
Total assets	264,745	257,954
Liabilities and shareholders' equity
Other liabilities	278	275
Junior subordinated debt	41,238	41,238
Total liabilities	41,516	41,513
Shareholders' equity:
Common stock, no par value: 50,000,000 shares authorized; issued and outstanding: 15,992,893 at June 30, 2012 15,978,958 at December 31, 2011	84,799	84,079
Retained earnings	134,893	128,551
Accumulated other comprehensive loss, net	3,537	3,811
Total shareholders' equity	223,229	216,441
Total liabilities and shareholders' equity	$ 264,745	$ 257,954