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Significant Accounting Policies - Noncurrent Deferred Tax Assets Recorded in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Equity [Abstract] |  |  |  |
Balance at beginning of period, Pension and Postretirement Benefit Plans | $ 78,619 | $ 79,675 | $ 79,938 | $ 82,044
Tax effect of other comprehensive earnings, Pension and Postretirement Benefit Plans | (1,326) | (1,193) | (2,645) | (3,562)
Balance at end of period, Pension and Postretirement Benefit Plans | 77,293 | 78,482 | 77,293 | 78,482
Balance at beginning of period, Unamortized Value of Terminated Forward Starting Interest Rate Swap |  | 464 | 178 | 749
Tax effect of other comprehensive earnings, Unamortized Value of Terminated Forward Starting Interest Rate Swap |  | (147) | (178) | (432)
Balance at end of period, Unamortized Value of Terminated Forward Starting Interest Rate Swap |  | 317 |  | 317
Balance at beginning of period, Net Noncurrent Deferred Tax Assets | 78,619 | 80,139 | 80,116 | 82,793
Tax effect of other comprehensive earnings, Net Noncurrent Deferred Tax Assets | (1,326) | (1,340) | (2,823) | (3,994)
Balance at end of period, Net Noncurrent Deferred Tax Assets | $ 77,293 | $ 78,799 | $ 77,293 | $ 78,799

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