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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, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Equity [Abstract] |  |  |  |
Balance at beginning of period, Pension and Postretirement Benefit Plans | $ 79,280 | $ 80,859 | $ 79,938 | $ 82,044
Tax effect of other comprehensive earnings, Pension and Postretirement Benefit Plans | (661) | (1,184) | (1,319) | (2,369)
Balance at end of period, Pension and Postretirement Benefit Plans | 78,619 | 79,675 | 78,619 | 79,675
Balance at beginning of period, Unamortized Value of Terminated Forward Starting Interest Rate Swap | 41 | 608 | 178 | 749
Tax effect of other comprehensive earnings, Unamortized Value of Terminated Forward Starting Interest Rate Swap | (41) | (144) | (178) | (285)
Balance at end of period, Unamortized Value of Terminated Forward Starting Interest Rate Swap |  | 464 |  | 464
Balance at beginning of period, Net Noncurrent Deferred Tax Assets | 79,321 | 81,467 | 80,116 | 82,793
Tax effect of other comprehensive earnings, Net Noncurrent Deferred Tax Assets | (702) | (1,328) | (1,497) | (2,654)
Balance at end of period, Net Noncurrent Deferred Tax Assets | $ 78,619 | $ 80,139 | $ 78,619 | $ 80,139

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