XML 97 R84.htm IDEA: XBRL DOCUMENT v3.8.0.1
Benefit Plans - Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rate (Detail) - Post-retirement [Member]
$ in Thousands
12 Months Ended
Dec. 31, 2017
USD ($)
Defined Benefit Plan Disclosure [Line Items]  
Effect on total service cost and interest cost, 1% increase $ 170
Effect on post-retirement benefits obligation, 1% increase 4,000
Effect on total service cost and interest cost, 1% decrease 140
Effect on post-retirement benefits obligation, 1% decrease $ 3,170