Quantitative Information about Level 3 Fair Value Measurements (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014
Auction Rate Securities
Fair Value Measurements [Line Items]
Level 3 Financial Instruments, asset	$ 26
Valuation Technique	Valuation Service / Broker Quotes
Unobservable Input	Broker quotes	[1]
EETC
Fair Value Measurements [Line Items]
Level 3 Financial Instruments, asset	59
Valuation Technique	Discounted Cash Flows
Unobservable Input	Structure credit risk	[2]
EETC | Structure Credit Risk
Fair Value Measurements [Line Items]
Level 3 fair value measurements, weighted average percentage	3.00%
Convertible Debt Derivative Asset
Fair Value Measurements [Line Items]
Level 3 Financial Instruments, asset	449
Valuation Technique	Binomial Lattice Model
Convertible Debt Derivative Asset | Expected Volatility
Fair Value Measurements [Line Items]
Level 3 fair value measurements, weighted average percentage	41.00%
Convertible Debt Derivative Asset | Own Credit Risk
Fair Value Measurements [Line Items]
Level 3 fair value measurements, weighted average percentage	5.00%
Convertible Debt Option Liability
Fair Value Measurements [Line Items]
Level 3 Financial Instruments, liability	$ (263)
Valuation Technique	Binomial Lattice Model
Convertible Debt Option Liability | Expected Volatility
Fair Value Measurements [Line Items]
Level 3 fair value measurements, weighted average percentage	42.00%
Convertible Debt Option Liability | Own Credit Risk
Fair Value Measurements [Line Items]
Level 3 fair value measurements, weighted average percentage	5.00%
Minimum | Convertible Debt Derivative Asset | Expected Volatility
Fair Value Measurements [Line Items]
Level 3 fair value measurements, percentage	40.00%
Minimum | Convertible Debt Option Liability | Expected Volatility
Fair Value Measurements [Line Items]
Level 3 fair value measurements, percentage	40.00%
Maximum | Convertible Debt Derivative Asset | Expected Volatility
Fair Value Measurements [Line Items]
Level 3 fair value measurements, percentage	60.00%
Maximum | Convertible Debt Option Liability | Expected Volatility
Fair Value Measurements [Line Items]
Level 3 fair value measurements, percentage	60.00%

[1] Broker quotes obtained by a third-party valuation service.

[2] Represents the credit risk premium of the EETC structure above the risk-free rate that the Company has determined market participants would use when pricing the instruments.