Fair Value Measurements - Fair Values of Note Payable and Long-Term Debt (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of note payable	$ 114	$ 39
Total	$ 1,175	$ 1,091
Senior Debentures 6.900 % Due 2028
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate	6.90%	6.90%
Debt instrument, year of maturity	2028	2028
Fair value of senior debt	$ 35	$ 34
Senior Debentures 6.920 % Due 2028
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate	6.92%	6.92%
Debt instrument, year of maturity	2028	2028
Fair value of senior debt	$ 525	$ 506
Senior Notes 6.125 % Due 2034
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Interest rate	6.125%	6.125%
Debt instrument, year of maturity	2034	2034
Fair value of senior debt	$ 501	$ 512
Quoted prices in active markets for identical assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of note payable	0	0
Total	0	0
Quoted prices in active markets for identical assets (Level 1) \| Senior Debentures 6.900 % Due 2028
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of senior debt	0	0
Quoted prices in active markets for identical assets (Level 1) \| Senior Debentures 6.920 % Due 2028
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of senior debt	0	0
Quoted prices in active markets for identical assets (Level 1) \| Senior Notes 6.125 % Due 2034
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of senior debt	0	0
Significant other observable inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of note payable	114	39
Total	1,175	1,091
Significant other observable inputs (Level 2) \| Senior Debentures 6.900 % Due 2028
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of senior debt	35	34
Significant other observable inputs (Level 2) \| Senior Debentures 6.920 % Due 2028
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of senior debt	525	506
Significant other observable inputs (Level 2) \| Senior Notes 6.125 % Due 2034
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of senior debt	501	512
Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of note payable	0	0
Total	0	0
Significant unobservable inputs (Level 3) \| Senior Debentures 6.900 % Due 2028
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of senior debt	0	0
Significant unobservable inputs (Level 3) \| Senior Debentures 6.920 % Due 2028
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of senior debt	0	0
Significant unobservable inputs (Level 3) \| Senior Notes 6.125 % Due 2034
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of senior debt	$ 0	$ 0

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611

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Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
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Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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No definition available.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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- Definition

Fair value portion of notes payable.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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