Description of Business and Summary of Significant Accounting Policies Recently issued accounting pronouncements not yet adopted (Details) - Accounting Standards Update 2016-02 [Member] $ in Millions	Jan. 01, 2019 USD ($)
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset	$ 140
Operating Lease, Liability	140
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset	150
Operating Lease, Liability	$ 150