Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Schedule of Assets and Liabilities Measured at Fair Value (Details)

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Summary of Significant Accounting Policies - Schedule of Assets and Liabilities Measured at Fair Value (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Mar. 31, 2018
Liabilities:    
Debt $ 6,987,473 $ 6,756,559
Level 1    
Liabilities:    
Debt 0 0
Level 2    
Liabilities:    
Debt 6,987,473 6,756,559
Level 3    
Liabilities:    
Debt 0 0
Pandora    
Assets:    
Fair value of investment 480,472 511,847
Pandora | Investee    
Liabilities:    
Investment in convertible preferred stock 480,000  
Pandora | Level 1    
Assets:    
Fair value of investment 0 0
Pandora | Level 2    
Assets:    
Fair value of investment 480,472 511,847
Pandora | Level 3    
Assets:    
Fair value of investment $ 0 $ 0