Leasing Activities (Narrative) (Detail) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2011	Jun. 30, 2012	Dec. 31, 2011
Leases [Line Items]
Lease investments			$ 1,400,000,000	$ 1,300,000,000
Aggregate cash proceeds	161,000,000
Lease termination payments	423,000,000
Pre-tax gain	39,000,000	39,000,000
Reversal of permanent tax benefits	22,000,000	22,000,000
After-tax gain	3,000,000	3,000,000
Income tax provision at statutory federal rate	$ 14,000,000	$ 14,000,000