Significant Accounting Policies - Noncurrent Deferred Tax Assets Recorded in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Equity [Abstract]
Balance at beginning of period, Pension and Postretirement Benefit Plans	$ 84,207	$ 79,938
Tax effect of other comprehensive earnings, Pension and Postretirement Benefit Plans	(868)	(658)
Balance at end of period, Pension and Postretirement Benefit Plans	83,339	79,280
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		(137)
Balance at end of period, Unamortized Value of Terminated Forward Starting Interest Rate Swap		41
Balance at beginning of period, Net Noncurrent Deferred Tax Assets	84,207	80,116
Tax effect of other comprehensive earnings, Net Noncurrent Deferred Tax Assets	(868)	(795)
Balance at end of period, Net Noncurrent Deferred Tax Assets	$ 83,339	$ 79,321