General and Summary of Significant Accounting Policies Change in Accounting Estimate (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Postretirement Benefit Costs [Member]
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	$ (2)
Postretirement Benefit Costs [Member] | UNITED STATES
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	(1)
Postretirement Benefit Costs [Member] | UNITED KINGDOM
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	(1)
Postretirement Benefit Costs [Member] | Disaggregated Rate Approach [Member]
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	16
Postretirement Benefit Costs [Member] | Disaggregated Rate Approach [Member] | UNITED STATES
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	13
Postretirement Benefit Costs [Member] | Disaggregated Rate Approach [Member] | UNITED KINGDOM
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	3
Postretirement Benefit Costs [Member] | Aggregated Rate Approach [Member]
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	18
Postretirement Benefit Costs [Member] | Aggregated Rate Approach [Member] | UNITED STATES
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	14
Postretirement Benefit Costs [Member] | Aggregated Rate Approach [Member] | UNITED KINGDOM
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	4
Interest Expense [Member]
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	(11)
Interest Expense [Member] | UNITED STATES
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	(9)
Interest Expense [Member] | UNITED KINGDOM
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	(2)
Interest Expense [Member] | Disaggregated Rate Approach [Member]
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	49
Interest Expense [Member] | Disaggregated Rate Approach [Member] | UNITED STATES
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	42
Interest Expense [Member] | Disaggregated Rate Approach [Member] | UNITED KINGDOM
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	7
Interest Expense [Member] | Aggregated Rate Approach [Member]
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	60
Interest Expense [Member] | Aggregated Rate Approach [Member] | UNITED STATES
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	51
Interest Expense [Member] | Aggregated Rate Approach [Member] | UNITED KINGDOM
Change in Accounting Estimate [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	$ 9