Noncurrent Deferred Tax Assets Recorded in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Equity [Abstract]
Balance at beginning of period, Pension and Postretirement Benefit Plans	$ 79,675	$ 66,931	$ 82,044	$ 66,467
Tax effect of other comprehensive earnings, Pension and Postretirement Benefit Plans	(1,193)	(986)	(3,562)	(522)
Balance at end of period, Pension and Postretirement Benefit Plans	78,482	65,945	78,482	65,945
Balance at beginning of period, Unamortized Value of Terminated Forward Starting Interest Rate Swap	464	1,023	749	1,290
Tax effect of other comprehensive earnings, Unamortized Value of Terminated Forward Starting Interest Rate Swap	(147)	(136)	(432)	(403)
Balance at end of period, Unamortized Value of Terminated Forward Starting Interest Rate Swap	317	887	317	887
Balance at beginning of period, Net Noncurrent Deferred Tax Assets	80,139	67,954	82,793	67,757
Tax effect of other comprehensive earnings, Net Noncurrent Deferred Tax Assets	(1,340)	(1,122)	(3,994)	(925)
Balance at end of period, Net Noncurrent Deferred Tax Assets	$ 78,799	$ 66,832	$ 78,799	$ 66,832