Pension and Postretirement Benefits Other Than Pension Plans - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Corporate Operating Expenses [Member]
Defined Benefit Plan Disclosure [Line Items]
Net settlement loss	$ 1,600	$ 1,600	$ 1,600	$ 1,600
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net settlement loss	$ 1,567	$ 1,593	$ 1,567	$ 1,593
Discount rate	3.10%		3.10%		3.90%
Increase in pension plan liability			$ 5,300