TriCo Bancshares Condensed Financial Statements (Parent Only) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Assets
Cash and Cash equivalents	$ 802,271	$ 748,899	$ 681,760	$ 637,275
Other assets	38,484	38,607
Total assets	2,612,433	2,609,269
Liabilities and shareholders' equity
Other liabilities	37,340	35,122
Junior subordinated debt	41,238	41,238
Total liabilities	2,376,403	2,379,910
Shareholders' equity:
Common stock, no par value: authorized 50,000,000 shares; issued and outstanding 16,005,191 and 16,000,838 shares, respectively	85,995	85,561
Retained earnings	148,497	141,639
Accumulated other comprehensive loss, net	1,538	2,159
Total shareholders' equity	236,030	229,359	219,038	216,441
Total liabilities and shareholders' equity	2,612,433	2,609,269
Parent [Member]
Assets
Cash and Cash equivalents	2,497	2,511	627	706
Investment in Tri Counties Bank	273,794	267,118
Other assets	1,238	1,238
Total assets	277,529	270,867
Liabilities and shareholders' equity
Other liabilities	261	270
Junior subordinated debt	41,238	41,238
Total liabilities	41,499	41,508
Shareholders' equity:
Common stock, no par value: authorized 50,000,000 shares; issued and outstanding 16,005,191 and 16,000,838 shares, respectively	85,995	85,561
Retained earnings	148,497	141,639
Accumulated other comprehensive loss, net	1,538	2,159
Total shareholders' equity	236,030	229,359
Total liabilities and shareholders' equity	$ 277,529	$ 270,867