TriCo Bancshares Condensed Financial Statements (Parent Only) - Condensed Balance Sheets (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Assets
Cash and Cash equivalents	$ 315,088	$ 303,461	$ 209,298	$ 610,728
Other assets	60,096	48,591
Total assets	4,467,131	4,220,722
Liabilities and shareholders' equity Other liabilities	69,695	65,293
Junior subordinated debt	56,617	56,470
Total liabilities	3,985,241	3,768,606
Shareholders' equity:
Common stock, no par value: authorized 50,000,000 shares; issued and outstanding 22,827,277 and 22,775,173 shares, respectively	250,290	247,587
Retained earnings	226,647	206,307
Accumulated other comprehensive income (loss), net	4,953	(1,778)
Total shareholders' equity	481,890	452,116	443,345	418,172
Total liabilities and shareholders' equity	4,467,131	4,220,722
Parent [Member]
Assets
Cash and Cash equivalents	2,768	2,565	$ 2,168	$ 2,229
Investment in Tri Counties Bank	534,399	504,655
Other assets	1,726	1,714
Total assets	538,893	508,934
Liabilities and shareholders' equity Other liabilities	386	348
Junior subordinated debt	56,617	56,470
Total liabilities	57,003	56,818
Shareholders' equity:
Common stock, no par value: authorized 50,000,000 shares; issued and outstanding 22,827,277 and 22,775,173 shares, respectively	250,290	247,587
Retained earnings	226,647	206,307
Accumulated other comprehensive income (loss), net	4,953	(1,778)
Total shareholders' equity	481,890	452,116
Total liabilities and shareholders' equity	$ 538,893	$ 508,934