Noncurrent Deferred Tax Assets Recorded in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Equity [Abstract]
Balance at beginning of period, Pension and Postretirement Benefit Plans	$ 80,859	$ 65,523	$ 82,044	$ 66,467
Tax effect of other comprehensive earnings, Pension and Postretirement Benefit Plans	(1,184)	1,408	(2,369)	464
Balance at end of period, Pension and Postretirement Benefit Plans	79,675	66,931	79,675	66,931
Balance at beginning of period, Unamortized Value of Terminated Forward Starting Interest Rate Swap	608	1,159	749	1,290
Tax effect of other comprehensive earnings, Unamortized Value of Terminated Forward Starting Interest Rate Swap	(144)	(136)	(285)	(267)
Balance at end of period, Unamortized Value of Terminated Forward Starting Interest Rate Swap	464	1,023	464	1,023
Balance at beginning of period, Net Noncurrent Deferred Tax Assets	81,467	66,682	82,793	67,757
Tax effect of other comprehensive earnings, Net Noncurrent Deferred Tax Assets	(1,328)	1,272	(2,654)	197
Balance at end of period, Net Noncurrent Deferred Tax Assets	$ 80,139	$ 67,954	$ 80,139	$ 67,954