Summary of Significant Accounting Policies - New Accounting Pronouncements (Details) - Accounting Standards Update 201602 - Restatement Adjustment [Member] $ in Millions	Dec. 31, 2018 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Initial lease liability	$ 80
Finance lease obligation	45
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Initial lease liability	$ 75