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CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Income Statement [Abstract]      
Facility depreciation and amortization $ 334,768 $ 349,215 $ 407,427
Non-cash stock-based compensation expense $ 20,747 $ 23,026 $ 26,067