XML 60 R47.htm IDEA: XBRL DOCUMENT v3.8.0.1
Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2002
Dec. 31, 2017
Property, Plant and Equipment [Line Items]    
Cash and cash equivalents maturity period, days   90 days
Percentage of participants matched contribution   6.00%
Dividends paid on unallocated ESOP shares over period (in years)   30 years
Shares held by the DDFP (in shares)   296,049
Service period of employee subjected to elimination of postretirement healthcare benefits (in years) 10 years  
Reclassification due to the adoption of ASU No. 2018-02   $ 0
Depositor Relationships [Member]    
Property, Plant and Equipment [Line Items]    
Amortized accelerated basis period (in years)   8 years 9 months 18 days
Building [Member] | Minimum [Member]    
Property, Plant and Equipment [Line Items]    
Estimated useful life, (in years)   25 years
Building [Member] | Maximum [Member]    
Property, Plant and Equipment [Line Items]    
Estimated useful life, (in years)   40 years
Furniture And Equipment [Member] | Minimum [Member]    
Property, Plant and Equipment [Line Items]    
Estimated useful life, (in years)   3 years
Furniture And Equipment [Member] | Maximum [Member]    
Property, Plant and Equipment [Line Items]    
Estimated useful life, (in years)   5 years
Beacon Trust [Member] | Customer Relationships [Member]    
Property, Plant and Equipment [Line Items]    
Amortized accelerated basis period (in years)   12 years
The MDE Group [Member] | Customer Relationships [Member]    
Property, Plant and Equipment [Line Items]    
Amortized accelerated basis period (in years)   10 years 4 months 24 days
Accounting Standards Update 2018-02 [Member] | New Accounting Pronouncement, Early Adoption, Effect [Member]    
Property, Plant and Equipment [Line Items]    
Reclassification due to the adoption of ASU No. 2018-02   $ 1,400