Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent	9.30%
Capital Loss Carryforward	$ 235
Cumulative Effect of New Accounting Principle in Period of Adoption		$ 9
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease Liability Expected	100
Operating Lease Right Of Use Asset Expected	$ 100