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Stock Options and Other Equity-Based Incentive Instruments - Additional Information (Detail) - USD ($)
6 Months Ended
Jun. 30, 2018
Dec. 31, 2017
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Outstanding options under the plan 428,900 446,400
Options currently not exercisable yet expected to vest 3,000  
Weighted-average remaining contractual term 1 year 3 months 18 days  
Pre-tax compensation costs expected to recognize $ 20,000  
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 69,636 68,457
Weighted-average remaining contractual term 1 year 6 months  
Pre-tax compensation costs $ 2,018,000  
Number of units released 25,398  
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 51,792 52,829
Weighted-average remaining contractual term 1 year 10 months 24 days  
Pre-tax compensation costs $ 1,116,000  
Number of units released 25,512  
Minimum [Member]    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Maximum aggregate number of shares of TriCo's common stock issued 650,000  
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]    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Maximum aggregate number of shares of TriCo's common stock issued 1,650,000  
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 77,689  
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 408,900  
Options available for grant under the plan 376,144  
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 121,428  
2001 Plan [Member]    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Outstanding options under the plan 20,000  
Options available for grant under the plan 0  
Share based compensation grant expiry period 10 years