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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-SubTopic 20
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Legal and Regulatory Proceedings (Legal and Regulatory Proceedings - Additional Information) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2013	Mar. 31, 2016 USD ($)	Sep. 30, 2015 USD ($)	Mar. 31, 2013 USD ($)	Sep. 30, 2012
Loss Contingencies
Class Settlement Escrow	$ 5,300
Amount in excess of amounts reserved	14
Litigation Settlement Amount	6,240
APR Percentage Allegedly Misleading						120.00%
Number Of Putative Class Actions Filed		4
Damages Claimed By Plaintiff	900		$ 40	$ 800
Settlement Payment Returned To Defendants	$ 700
Federal Lawsuits
Loss Contingencies
Number of merchants requesting exclusion	500
Class Action Settlement
Loss Contingencies
Number of merchants requesting exclusion	8,000
Percentage of escrow funds returned to defendants	25.00%
Escrow Deposit					$ 46