Business Segments and Geographic Areas - Summary of Company's Revenues from External Customers and Long-Lived Assets, by Geographical Areas (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total operating revenues	$ 148,336	$ 150,167	$ 146,424	$ 134,618	$ 144,853	$ 158,093	$ 167,136	$ 164,016	$ 579,545	$ 634,098	$ 804,228
Total Long-Lived Assets	946,765				903,977				946,765	903,977
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total operating revenues									530,115	579,300	722,339
Total Long-Lived Assets	601,530				751,290				601,530	751,290
International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total operating revenues									49,430	54,798	$ 81,889
Total Long-Lived Assets	$ 345,235				$ 152,687				$ 345,235	$ 152,687