Income Taxes - Federal and State Net Operating Loss and Tax Credit Carryovers (Details) $ in Millions	Dec. 31, 2019 USD ($)
U.S.
Income Taxes
Net operating loss carryover	$ 2,953
U.S. \| 2031 - 2037
Income Taxes
Net operating loss carryover	2,524
U.S. \| No Expiration
Income Taxes
Net operating loss carryover	429
State \| 2026 - 2038
Income Taxes
Net operating loss carryover	$ 480

Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319

Name:	us-gaap_OperatingLossCarryforwards
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant