Noncurrent Deferred Tax Assets Recorded in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Equity [Abstract]
Balance at beginning of period, Pension and Postretirement Benefit Plans	$ 79,938	$ 82,044
Tax effect of other comprehensive earnings, Pension and Postretirement Benefit Plans	(658)	(1,185)
Balance at end of period, Pension and Postretirement Benefit Plans	79,280	80,859
Balance at beginning of period, Unamortized Value of Terminated Forward Starting Interest Rate Swap	178	749
Tax effect of other comprehensive earnings, Unamortized Value of Terminated Forward Starting Interest Rate Swap	(137)	(141)
Balance at end of period, Unamortized Value of Terminated Forward Starting Interest Rate Swap	41	608
Balance at beginning of period, Net Noncurrent Deferred Tax Assets	80,116	82,793
Tax effect of other comprehensive earnings, Net Noncurrent Deferred Tax Assets	(795)	(1,326)
Balance at end of period, Net Noncurrent Deferred Tax Assets	$ 79,321	$ 81,467