XML 119 R97.htm IDEA: XBRL DOCUMENT v3.7.0.1
Postretirement Benefit Plans (Amounts Recognized in Balance Sheet) (Detail) - USD ($)
$ in Thousands
Dec. 31, 2016
Dec. 31, 2015
Defined Benefit Postretirement Health And Life Coverage [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Accrued benefit liability $ 540 $ 572
Director's Retirement Plan [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Accrued benefit liability $ 1,122 $ 1,150