Composition of Certain Balance Sheet Accounts - Property and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 854,876	$ 816,989
Accumulated depreciation	(312,438)	(297,179)
Property and equipment, net	542,438	519,810
Office Equipment, Furniture, Fixtures and Other [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	51,699	49,529
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	42,173	42,143
Airborne Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	585,675	557,196
Network Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 175,329	$ 168,121