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Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Thousands
9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]      
Restricted Cash $ 18,981 $ 5,102 $ 25,336
Payment for Debt Extinguishment or Debt Prepayment Cost $ 0 $ 1,453  
Capitalized Initial Direct Costs $ 0.01