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Stock Options and Other Equity-Based Incentive Instruments - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Outstanding options under the plan 446,400 592,250
Options currently not exercisable yet expected to vest 24,300  
Weighted-average remaining contractual term 8 months 12 days  
Pre-tax compensation costs expected to recognize $ 108,000  
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 68,457 68,450
Weighted-average remaining contractual term 1 year 2 months 12 days  
Pre-tax compensation costs $ 1,448,000  
Number of units released 30,896  
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 52,829 47,426
Weighted-average remaining contractual term 1 year 4 months 24 days  
Pre-tax compensation costs $ 724,000  
Number of units released 18,805  
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 79,243  
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 411,900  
Options available for grant under the plan 527,039  
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 121,286  
2001 Plan [Member]    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Outstanding options under the plan 34,500  
Options available for grant under the plan 0  
Share based compensation grant expiry period 10 years