Business, Basis of Presentation and Summary of Significant Accounting Policies (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 31, 2018 USD ($) segment	Dec. 31, 2017 USD ($)	Aug. 04, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of segments	3	3
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets			$ 20
Spinoff
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common Stock Distribution by Parent				80.80%
Parent percentage [Member] | Spinoff
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common Stock Retained by Parent				19.20%
AOCI Attributable to Parent [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	$ 15	$ 15	(15)
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets			$ 35
Retained Earnings [Member] | Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	$ 38	$ 38