Summary of Significant Accounting Policies (New Accounting Standards) (Expected Impact of Adoption of ASU 2016-02) (Details) - Accounting Standards Update 2016-02 [Member] $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
New Accounting Pronouncements or Change in Accounting Principle
Operating Lease Right of Use Asset, Expected	$ 60
Operating Lease Liability, Expected	$ 65