TriCo Bancshares Condensed Financial Statements (Parent Only) - Condensed Balance Sheets (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Assets
Cash and Cash equivalents	$ 209,298	$ 610,728	$ 369,679	$ 598,368
Other assets	47,360	51,735
Total assets	4,021,628	3,916,458
Liabilities and shareholders' equity
Other liabilities	54,252	49,192
Junior subordinated debt	56,420	56,272
Total liabilities	3,578,283	3,498,286
Shareholders' equity:
Common stock, no par value: authorized 50,000,000 shares; issued and outstanding 22,764,295 and 22,714,964 shares, respectively	246,312	244,318
Retained earnings	199,331	176,057
Accumulated other comprehensive loss, net	(2,298)	(2,203)
Total shareholders' equity	443,345	418,172	267,380	250,946
Total liabilities and shareholders' equity	4,021,628	3,916,458
Parent [Member]
Assets
Cash and Cash equivalents	2,168	2,229	$ 2,022	$ 2,520
Investment in Tri Counties Bank	496,336	470,797
Other assets	1,746	1,902
Total assets	500,250	474,928
Liabilities and shareholders' equity
Other liabilities	485	484
Junior subordinated debt	56,420	56,272
Total liabilities	56,905	56,756
Shareholders' equity:
Common stock, no par value: authorized 50,000,000 shares; issued and outstanding 22,764,295 and 22,714,964 shares, respectively	246,312	244,318
Retained earnings	199,331	176,057
Accumulated other comprehensive loss, net	(2,298)	(2,203)
Total shareholders' equity	443,345	418,172
Total liabilities and shareholders' equity	$ 500,250	$ 474,928