Significant Accounting Policies - Noncurrent Deferred Tax Assets Recorded in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Equity [Abstract]
Balance at beginning of period, Net Noncurrent Deferred Tax Assets	$ 82,417	$ 78,619	$ 84,207	$ 80,116
Tax effect of other comprehensive earnings, Net Noncurrent Deferred Tax Assets	(899)	(1,326)	(2,689)	(2,823)
Balance at end of period, Net Noncurrent Deferred Tax Assets	81,518	77,293	81,518	77,293
Balance at beginning of period, Pension and Postretirement Benefit Plans	82,417	78,619	84,207	79,938
Tax effect of other comprehensive earnings, Pension and Postretirement Benefit Plans	(899)	(1,326)	(2,689)	(2,645)
Balance at end of period, Pension and Postretirement Benefit Plans	$ 81,518	$ 77,293	$ 81,518	77,293
Balance at beginning of period, Unamortized Value of Terminated Forward Starting Interest Rate Swap				178
Tax effect of other comprehensive earnings, Unamortized Value of Terminated Forward Starting Interest Rate Swap				$ (178)