Income Taxes Level 4 (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation Allowance [Line Items]
Valuation allowance	$ (547)	$ (522)	$ (651)	$ (611)
Income tax benefit	(40)	(18)	(38)
Disallowed interest expense carryforward	0
Global Intangible low tax income	0
Changes in enacted tax laws and tax rates	0	167	0
Transition tax expense	$ 0	65	$ 0
Valuation allowance, deferred tax asset, decrease amount		$ 234