TriCo Bancshares Condensed Financial Statements (Parent Only) - Condensed Balance Sheets (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Assets
Cash and Cash equivalents	$ 281,228,000	$ 610,728,000	$ 502,251,000	$ 598,368,000
Other assets	51,002,000	51,735,000
Total assets	3,895,860,000	3,916,458,000
Liabilities and shareholders' equity
Other liabilities	53,256,000	49,192,000
Junior subordinated debt	56,320,000	56,272,000
Total liabilities	3,471,027,000	3,498,286,000
Shareholders' equity:
Common stock, no par value: authorized 50,000,000 shares; issued and outstanding 22,740,503 and 22,714,964 shares, respectively	245,316,000	244,318,000
Retained earnings	181,600,000	176,057,000
Accumulated other comprehensive loss, net	(2,083,000)	(2,203,000)
Total shareholders' equity	424,833,000	418,172,000	256,977,000	250,946,000
Total liabilities and shareholders' equity	3,895,860,000	3,916,458,000
Parent [Member]
Assets
Cash and Cash equivalents	2,044,000	2,229,000	2,383,000	2,520,000
Investment in Tri Counties Bank	477,845,000	470,797,000
Other assets	1,738,000	1,902,000
Total assets	481,627,000	474,928,000
Liabilities and shareholders' equity
Other liabilities	474,000	484,000
Junior subordinated debt	56,320,000	56,272,000
Total liabilities	56,794,000	56,756,000
Shareholders' equity:
Common stock, no par value: authorized 50,000,000 shares; issued and outstanding 22,740,503 and 22,714,964 shares, respectively	245,316,000	244,318,000
Retained earnings	181,600,000	176,057,000
Accumulated other comprehensive loss, net	(2,083,000)	(2,203,000)
Total shareholders' equity	424,833,000	418,172,000
Total liabilities and shareholders' equity	$ 481,627,000	$ 474,928,000