Income Taxes - Tax Effects, Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred tax liabilities:
Property	$ 0	$ (70)
Investment in partnership	(133)	(7)
Other	0	(4)
Total deferred tax liabilities	(133)	(81)
Deferred tax asset:
Net operating loss	228	184
Tax credit carryforwards	3	8
Other	0	8
Valuation allowance	(2)	(1)
Total deferred tax asset	229	199
Net deferred tax asset	$ 96	$ 118