TriCo Bancshares Condensed Financial Statements (Parent Only) - Condensed Balance Sheets (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Assets
Cash and Cash equivalents	$ 369,679	$ 598,368	$ 541,150	$ 748,899
Other assets	34,571	36,086
Total assets	2,794,943	2,744,066
Liabilities and shareholders' equity
Other liabilities	33,331	31,711
Junior subordinated debt	41,238	41,238
Total liabilities	2,527,563	2,493,120
Shareholders' equity:
Common stock, no par value: authorized 50,000,000 shares; issued and outstanding 16,139,414 and 16,076,662 shares, respectively	92,692	89,356
Retained earnings	172,892	159,733
Accumulated other comprehensive income, net	1,796	1,857
Total shareholders' equity	267,380	250,946	245,452	229,359
Total liabilities and shareholders' equity	2,794,943	2,744,066
Parent [Member]
Assets
Cash and Cash equivalents	2,022	2,520	2,489	2,511
Investment in Tri Counties Bank	305,543	288,746
Other assets	1,465	1,280
Total assets	309,030	292,546
Liabilities and shareholders' equity
Other liabilities	412	362
Junior subordinated debt	41,238	41,238
Total liabilities	41,650	41,600
Shareholders' equity:
Common stock, no par value: authorized 50,000,000 shares; issued and outstanding 16,139,414 and 16,076,662 shares, respectively	92,692	89,356
Retained earnings	172,892	159,733
Accumulated other comprehensive income, net	1,796	1,857
Total shareholders' equity	267,380	250,946
Total liabilities and shareholders' equity	$ 309,030	$ 292,546