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CONSOLIDATED BALANCE SHEETS (unaudited) (Parenthetical) - USD ($)
shares in Thousands, $ in Thousands
Sep. 30, 2021
Dec. 31, 2020
Statement of Financial Position [Abstract]    
Property and equipment, accumulated depreciation $ 4,838,262 $ 4,480,429
Intangible assets, accumulated amortization $ 66,455 $ 70,141
Preferred stock, par value (usd per share) $ 0.001 $ 0.001
Preferred stock, shares authorized (in shares) 5,000 5,000
Preferred stock, issued (in shares) 0 0
Common stock, par value (usd per share) $ 0.001 $ 0.001
Common stock, shares authorized (in shares) 450,000 450,000
Common stock, shares issued (in shares) 110,886 109,933
Common stock, shares outstanding (in shares) 103,136 109,933
Treasury Stock, Common, Shares 7,750 0