Revenue from Contracts with Customers - Summary of Comparison of Selected Unaudited Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Unaudited Condensed Consolidated Balance Sheets
Prepaid and other current assets	$ 154,408	$ 158,236	$ 157,625
Other assets	71,389	104,383	102,276
Accrued liabilities	130,123		154,655
Deferred tax liability	124,350	184,828	167,299
Retained earnings	1,899,735	$ 1,949,686	$ 1,964,497
Adjustments [Member] | Accounting Standards Update 2014-09 [Member]
Unaudited Condensed Consolidated Balance Sheets
Prepaid and other current assets	(1,174)
Other assets	(2,107)
Accrued liabilities	739
Deferred tax liability	(402)
Retained earnings	(3,619)
Balance Without Adoption of Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Unaudited Condensed Consolidated Balance Sheets
Prepaid and other current assets	153,234
Other assets	69,282
Accrued liabilities	130,862
Deferred tax liability	123,948
Retained earnings	$ 1,896,116