Other Material Contingencies - Total Guarantees (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Guarantor Obligations [Line Items]
Total guarantees, by type and term	$ 1,500	$ 1,331
Energy Transactions [Member]
Guarantor Obligations [Line Items]
Total guarantees, by type and term	888
Solar Energy Projects [Member]
Guarantor Obligations [Line Items]
Total guarantees, by type and term	581
Other [Member]
Guarantor Obligations [Line Items]
Total guarantees, by type and term	31
0 - 3 years [Member]
Guarantor Obligations [Line Items]
Total guarantees, by type and term	1,384
0 - 3 years [Member] | Energy Transactions [Member]
Guarantor Obligations [Line Items]
Total guarantees, by type and term	785
0 - 3 years [Member] | Solar Energy Projects [Member]
Guarantor Obligations [Line Items]
Total guarantees, by type and term	568
0 - 3 years [Member] | Other [Member]
Guarantor Obligations [Line Items]
Total guarantees, by type and term	31
4 - 10 years [Member]
Guarantor Obligations [Line Items]
Total guarantees, by type and term	48
4 - 10 years [Member] | Energy Transactions [Member]
Guarantor Obligations [Line Items]
Total guarantees, by type and term	35
4 - 10 years [Member] | Solar Energy Projects [Member]
Guarantor Obligations [Line Items]
Total guarantees, by type and term	13
4 - 10 years [Member] | Other [Member]
Guarantor Obligations [Line Items]
Total guarantees, by type and term
Greater than 10 years [Member]
Guarantor Obligations [Line Items]
Total guarantees, by type and term	68
Greater than 10 years [Member] | Energy Transactions [Member]
Guarantor Obligations [Line Items]
Total guarantees, by type and term	68
Greater than 10 years [Member] | Solar Energy Projects [Member]
Guarantor Obligations [Line Items]
Total guarantees, by type and term
Greater than 10 years [Member] | Other [Member]
Guarantor Obligations [Line Items]
Total guarantees, by type and term