Fair Value Measurements - Valuation of Financial Instruments that are Marked-to-Market on Recurring Basis (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Available-for-sale investments:
Available-for-sale investments	$ 4	$ 5
Derivative assets	1,109	728
Derivative liabilities	(1,611)	(1,515)
Interest Rate Swaps [Member]
Available-for-sale investments:
Derivative assets	1,098	726
Derivative liabilities	(345)	(160)
Cross-Currency Interest Rate Swaps [Member]
Available-for-sale investments:
Derivative assets	10	2
Derivative liabilities	(852)	(988)
Other [Member]
Available-for-sale investments:
Derivative assets	1
Derivative liabilities	(8)	(2)
Floor Income Contracts [Member]
Available-for-sale investments:
Derivative liabilities	(406)	(365)
Fair Value Measurements Recurring [Member]
Available-for-sale investments:
Available-for-sale investments	4	5
Derivative assets	1,109	728
Total	1,113	733
Derivative liabilities	(1,611)	(1,515)
Total	(1,611)	(1,515)
Fair Value Measurements Recurring [Member] \| Interest Rate Swaps [Member]
Available-for-sale investments:
Derivative assets	1,098	726
Derivative liabilities	(345)	(160)
Fair Value Measurements Recurring [Member] \| Cross-Currency Interest Rate Swaps [Member]
Available-for-sale investments:
Derivative assets	10	2
Derivative liabilities	(852)	(988)
Fair Value Measurements Recurring [Member] \| Other [Member]
Available-for-sale investments:
Derivative assets	1
Derivative liabilities	(8)	(2)
Fair Value Measurements Recurring [Member] \| Floor Income Contracts [Member]
Available-for-sale investments:
Derivative liabilities	(406)	(365)
Fair Value Measurements Recurring [Member] \| Agency Residential Mortgage-Backed Securities [Member]
Available-for-sale investments:
Available-for-sale investments	1	1
Fair Value Measurements Recurring [Member] \| Other [Member]
Available-for-sale investments:
Available-for-sale investments	3	4
Level 2 [Member] \| Fair Value Measurements Recurring [Member]
Available-for-sale investments:
Available-for-sale investments	4	5
Derivative assets	1,070	709
Total	1,074	714
Derivative liabilities	(727)	(547)
Total	(727)	(547)
Level 2 [Member] \| Fair Value Measurements Recurring [Member] \| Interest Rate Swaps [Member]
Available-for-sale investments:
Derivative assets	1,070	709
Derivative liabilities	(280)	(99)
Level 2 [Member] \| Fair Value Measurements Recurring [Member] \| Cross-Currency Interest Rate Swaps [Member]
Available-for-sale investments:
Derivative liabilities	(41)	(83)
Level 2 [Member] \| Fair Value Measurements Recurring [Member] \| Floor Income Contracts [Member]
Available-for-sale investments:
Derivative liabilities	(406)	(365)
Level 2 [Member] \| Fair Value Measurements Recurring [Member] \| Agency Residential Mortgage-Backed Securities [Member]
Available-for-sale investments:
Available-for-sale investments	1	1
Level 2 [Member] \| Fair Value Measurements Recurring [Member] \| Other [Member]
Available-for-sale investments:
Available-for-sale investments	3	4
Level 3 [Member] \| Fair Value Measurements Recurring [Member]
Available-for-sale investments:
Derivative assets	39	19
Total	39	19
Derivative liabilities	(884)	(968)
Total	(884)	(968)
Level 3 [Member] \| Fair Value Measurements Recurring [Member] \| Interest Rate Swaps [Member]
Available-for-sale investments:
Derivative assets	28	17
Derivative liabilities	(65)	(61)
Level 3 [Member] \| Fair Value Measurements Recurring [Member] \| Cross-Currency Interest Rate Swaps [Member]
Available-for-sale investments:
Derivative assets	10	2
Derivative liabilities	(811)	(905)
Level 3 [Member] \| Fair Value Measurements Recurring [Member] \| Other [Member]
Available-for-sale investments:
Derivative assets	1
Derivative liabilities	$ (8)	$ (2)

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Fair value of financial and nonfinancial obligations.

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