Background (Details) $ in Millions	9 Months Ended
Sep. 30, 2019 state segment	Jan. 01, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of states in which entity operates \| state	14
Number of reportable segments \| segment	1
RETAINED EARNINGS (ACCUMULATED DEFICIT) \| Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative net effect of adoption of ASU		$ 126
Cumulative effect of new accounting principle in period of adoption, tax		$ 133

Cumulative Effect of New Accounting Principle in Period of Adoption, Tax

No definition available.

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- Definition

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
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- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

No definition available.

+ Details

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- Definition

The number of states the entity operates in as of the balance sheet date.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
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Period Type:	instant

- Details

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Namespace Prefix:
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- Details

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Balance Type:
Period Type: