CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Depreciation and amortization	$ 430,288	$ 469,388	$ 684,448
Non-cash stock-based compensation expense	$ 27,832	$ 32,285	$ 31,651