Geographic Information for Long-Lived Assets and Revenues in United States and other Countries (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:
Revenues	$ 60,341	$ 50,173	$ 43,572	$ 34,670	$ 29,058	$ 20,241	$ 20,651	$ 33,102	$ 188,756	$ 103,051	$ 279,574
Reportable Geographical Components [Member]
Long-lived assets:
Long-lived assets	333,147				499,615				333,147	499,615	543,838
Revenues:
Revenues									188,756	103,051	279,574
Reportable Geographical Components [Member] | UNITED STATES
Long-lived assets:
Long-lived assets	326,665				489,374				326,665	489,374	531,518
Revenues:
Revenues									149,040	67,609	199,187
Reportable Geographical Components [Member] | International
Long-lived assets:
Long-lived assets	$ 6,482				$ 10,241				6,482	10,241	12,320
Reportable Geographical Components [Member] | CANADA
Revenues:
Revenues									7,439	7,460	33,614
Reportable Geographical Components [Member] | Other International
Revenues:
Revenues									$ 32,276	$ 27,982	$ 46,773