Note 6 - Employee Benefit Plans (Detail) - Estimated Amortization Out of Regulatory Assets or Accumulated OCI (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Net Regulatory Assets [Member] | Pension Plans [Member]
Amortization of prior service credit	$ 0
Amortization of net loss	9
Net Regulatory Assets [Member] | Other Retirement Plans [Member]
Amortization of prior service credit	(3)
Amortization of net loss	6
Accumulated AOCI [Member] | Pension Plans [Member]
Amortization of prior service credit	(2)
Amortization of net loss	24
Accumulated AOCI [Member] | Other Retirement Plans [Member]
Amortization of prior service credit	(2)
Amortization of net loss	3
Total Net Regulatory Assets and AOCI [Member] | Pension Plans [Member]
Amortization of prior service credit	(2)
Amortization of net loss	33
Total Net Regulatory Assets and AOCI [Member] | Other Retirement Plans [Member]
Amortization of prior service credit	(5)
Amortization of net loss	$ 8