Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Schedule of Jointly Owned Utility Plants

The following table summarizes our proportionate ownership interest in jointly-owned power plants:

As of December 31, 2019	Ownership Interest		Property, Plant & Equipment		Accumulated Depreciation			Construction in Progress
(in millions, except percentages)
Freestone Energy Center	75.0	%	$	379	$	(177	)	$	—
Hidalgo Energy Center	78.5	%	$	250	$	(113	)	$	—

Schedule of Components of Restricted Cash

The table below represents the components of our restricted cash as of December 31, 2019 and 2018 (in millions):

	2019						2018
	Current		Non-Current		Total		Current		Non-Current		Total
Debt service	$	58	$	8	$	66	$	13	$	8	$	21
Construction/major maintenance	28		6		34		23		24		47
Security/project/insurance	209		31		240		120		—		120
Other	4		1		5		11		2		13
Total	$	299	$	46	$	345	$	167	$	34	$	201

Schedule of Intangible Assets and Goodwill [Table Text Block]

As of December 31, 2019 and 2018, the components of our intangible assets were as follows (in millions):

	2019		2018		Lives
Acquired contracts	$	444	$	458	0 – 9 Years
Customer relationships	445		445		7 – 14 Years
Trademark and trade name	40		40		15 Years
Other	4		88		39 – 44 Years
	933		1,031
Less: Accumulated amortization	593		619
Intangible assets, net	$	340	$	412

Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]

The estimated aggregate amortization expense of our intangible assets for the next five years is as follows (in millions):

2020	$	44
2021	$	39
2022	$	36
2023	$	28
2024	$	28