Fair Value Measurements - Carrying Amount and Estimated Fair Values of Financial Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Cash and cash equivalents, carrying amount	$ 140,849	$ 160,596	$ 86,709	$ 109,857
Interest rate swaps, carrying amount	1,169	9,803
Long-term debt, carrying amount	1,687,961	1,699,950
Cash and cash equivalents, fair value	140,849	160,596
Interest rate swaps, fair value	1,169	9,803
Long-term debt, fair value	$ 1,705,592	$ 1,716,815