Overview and Basis of Presentation - Summary of Cash and Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 136,631	$ 128,697	$ 162,422	$ 343,734
Cash and Cash Equivalents and Restricted Cash	138,567	130,231	163,443	344,805
Other Current Assets [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash included in "Other current assets"	566	149	153	154
Deferred Charges and Other Assets [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash included in "Deferred charges and other assets"	$ 1,370	$ 1,385	$ 868	$ 917