TriCo Bancshares Condensed Financial Statements (Parent Only) - Condensed Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 276,507	$ 227,533
Other assets	70,591	75,364
Total assets	6,471,181	6,352,441
Liabilities and shareholders' equity
Other liabilities	91,984	83,724
Junior subordinated debt	57,232	57,042
Total liabilities	5,564,611	5,525,068
Shareholders' equity
Preferred stock, no par value: 1,000,000 shares authorized, zero issued and outstanding at December 31, 2018 and 2017	0	0
Common stock, no par value: authorized 50,000,000 shares; issued and outstanding 30,417,223 and 22,955,963 shares at December 31, 2018 and 2017, respectively	543,998	541,762
Retained earnings	367,794	303,490
Accumulated other comprehensive loss, net	(5,222)	(17,879)
Total shareholders’ equity	906,570	827,373	$ 505,808	$ 477,347
Total liabilities and shareholders’ equity	6,471,181	6,352,441
Parent
Assets
Cash and cash equivalents	5,008	2,374
Investment in Tri Counties Bank	957,544	880,907
Other assets	1,765	1,723
Total assets	964,317	885,004
Liabilities and shareholders' equity
Other liabilities	515	589
Junior subordinated debt	57,232	57,042
Total liabilities	57,747	57,631
Shareholders' equity
Preferred stock, no par value: 1,000,000 shares authorized, zero issued and outstanding at December 31, 2018 and 2017	0	0
Common stock, no par value: authorized 50,000,000 shares; issued and outstanding 30,417,223 and 22,955,963 shares at December 31, 2018 and 2017, respectively	543,998	541,762
Retained earnings	367,794	303,490
Accumulated other comprehensive loss, net	(5,222)	(17,879)
Total shareholders’ equity	906,570	827,373
Total liabilities and shareholders’ equity	$ 964,317	$ 885,004