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Fair Value Measurements - Narrative (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Fair Value Disclosures [Abstract]          
Asset impairments $ 2,500 $ 1,800 $ 9,344 $ 13,653  
Estimated fair value of long-term debt 2,840,000 2,700,000 2,840,000 2,700,000 $ 2,490,000
Carrying value of long-term debt $ 2,900,000 $ 2,900,000 $ 2,900,000 $ 2,900,000 $ 2,900,000