Common and Preferred Stock (Schedule of Share Repurchases) (Detail) - USD ($) $ / shares in Units, $ in Millions	2 Months Ended	12 Months Ended
Feb. 20, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Share Repurchases [Abstract]
Number of shares repurchased	3,000,000.0	11,100,000	5,800,000	43,000,000.0
Average price paid per share	$ 9.18	$ 9.12	$ 8.21	$ 7.55
Remaining authorization as of December 31	$ 74	$ 101	$ 202	$ 250

Number of shares that have been repurchased during the period and are being held in treasury.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section S99
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration