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Stock Options and Other Equity-Based Incentive Instruments - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Aggregate number of shares of TriCo's common stock issued 1,650,000 650,000
Outstanding options under the plan 343,000 446,400
Options currently not exercisable yet expected to vest 1,125  
Weighted-average remaining contractual term 9 months 18 days  
Restricted Stock Units (RSUs) [Member] | Market Plus Service Condition Vesting RSUs [Member]    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Number of units outstanding expected to vest 45,536 52,829
Weighted-average remaining contractual term 1 year 4 months 24 days  
Pre-tax compensation costs $ 848,000  
Number of units released 25,512  
Restricted Stock Units (RSUs) [Member] | Service Condition Vesting RSUs [Member]    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Number of units outstanding expected to vest 66,947 68,457
Weighted-average remaining contractual term 1 year 4 months 24 days  
Pre-tax compensation costs $ 2,319,000  
Number of units released 35,060  
Minimum [Member] | Restricted Stock Units (RSUs) [Member] | Market Plus Service Condition Vesting RSUs [Member]    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Number of units released 0  
Maximum [Member] | Restricted Stock Units (RSUs) [Member] | Market Plus Service Condition Vesting RSUs [Member]    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Number of units released 68,304  
2009 Plan [Member]    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Number of shares to be reduced pursuant to stock option for computation of available number of shares for issuance 1  
Number of shares to be reduced pursuant to restricted stock award for computation of available number of shares for issuance 2  
Outstanding options under the plan 343,000  
Options available for grant under the plan 380,958  
2009 Plan [Member] | Restricted Stock Units (RSUs) [Member]    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Number of units outstanding expected to vest 112,483  
2001 Plan [Member]    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Outstanding options under the plan 10,000  
Options available for grant under the plan 0  
Share based compensation grant expiry period 10 years