Significant Accounting Policies - Noncurrent Deferred Tax Assets Recorded in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Equity [Abstract]
Balance at beginning of period, Net Noncurrent Deferred Tax Assets	$ 83,339	$ 79,321	$ 84,207	$ 80,116
Tax effect of other comprehensive earnings, Net Noncurrent Deferred Tax Assets	(922)	(702)	(1,790)	(1,497)
Balance at end of period, Net Noncurrent Deferred Tax Assets	82,417	78,619	82,417	78,619
Tax effect of other comprehensive earnings, Net Noncurrent Deferred Tax Assets	922	702	1,790	1,497
Balance at beginning of period, Pension and Postretirement Benefit Plans	83,339	79,280	84,207	79,938
Tax effect of other comprehensive earnings, Pension and Postretirement Benefit Plans	(922)	(661)	(1,790)	(1,319)
Balance at end of period, Pension and Postretirement Benefit Plans	$ 82,417	78,619	$ 82,417	78,619
Balance at beginning of period, Unamortized Value of Terminated Forward Starting Interest Rate Swap		41		178
Tax effect of other comprehensive earnings, Unamortized Value of Terminated Forward Starting Interest Rate Swap		$ (41)		$ (178)