Employee Benefit Plans - Additional Information (Detail) (USD $)
0 Months Ended 12 Months Ended 60 Months Ended
Aug. 19, 2008
Dec. 31, 2013
Age
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2009
Dec. 31, 2013
Employee Benefit Plan [Line Items]            
Qualification criteria minimum age   18        
Service period   3 months        
Employer contribution, employee retirement plan   3.00%        
Employee retirement plan, employer matching contribution   50.00%        
Employee's compensation contribution   6.00%        
Expense attributable to retirement benefit plan   $ 1,300,000 $ 1,100,000 $ 970,000    
Accrued liability for retirement benefit agreement   4,500,000 3,500,000     4,500,000
Equity Incentive Plan, issued 1,035,000          
Restricted stock awards, issued 414,000          
Restricted stock awards, delivered 414,000          
Number of common stock repurchased   287,652     414,000 1,691,580
Common stock repurchased cost         3,700,000  
Stock options and restricted shares granted date to employees and directors     5 years      
Weighted average grant date fair value of options granted   289,000 77,000 208,000    
Aggregate intrinsic value of stock outstanding   11,700,000       11,700,000
Aggregate intrinsic value of exercisable options   10,000,000       10,000,000
Aggregate intrinsic value of share   $ 22.58       $ 22.58
Compensation expense related to Share-Based Compensation Plan   1,200,000 1,200,000 1,100,000    
Tax benefit related to Share-Based Compensation Plan   325,000 309,000 288,000    
Proceeds on loan from the Company's subsidiary, Meridian Interstate Funding Corporation   8,300,000        
Maturity period of loan   20 years        
Loan payable rate   6.50%       6.50%
Fair value of the unallocated shares   13,100,000 10,400,000     13,100,000
Compensation expense recognized in connection with the ESOP   814,000 606,000 532,000    
Post-retirement benefit expenses   567,000 388,000 241,000    
Incentive compensation plan expense   3,300,000 3,100,000 1,900,000    
Subsidiaries [Member]
           
Employee Benefit Plan [Line Items]            
Number of shares ESOP acquired   828,000        
Supplemental Executive Retirement Benefits [Member]
           
Employee Benefit Plan [Line Items]            
Expected future benefit payments for the plan 2015   833,000       833,000
Expected future benefit payments for the plan 2019 through 2023   561,000       561,000
Restricted Stock [Member]
           
Employee Benefit Plan [Line Items]            
Restricted stock awards   35,520       35,520
Fair value of restricted shares vested, total   1,400,000        
Unrecognized compensation expense related to non-vested options under the plan   2,000,000       2,000,000
Cost expected to recognize weighted-average period   3 years 3 months 18 days        
Stock Option [Member]
           
Employee Benefit Plan [Line Items]            
Restricted stock awards   62,450       62,450
2008 Equity Incentive Plan [Member]
           
Employee Benefit Plan [Line Items]            
Equity Incentive Plan award, delivered 1,449,000          
Officer and Director [Member]
           
Employee Benefit Plan [Line Items]            
Supplemental executive retirement benefit expense for officers and directors   $ 1,200,000 $ 1,000,000 $ 791,000