Consolidated Statements of Shareholders' Equity (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income tax benefit on unrealized gain on marketable securities	$ 0	$ 0	$ 13
Income tax benefit on unrecognized prior service cost	5	0	20
Accumulated Other Comprehensive Income
Income tax benefit on unrealized gain on marketable securities	0	0	13
Net of income tax unrealized (loss) on interest rate swaps	0
Income tax benefit on unrecognized prior service cost	$ 5	$ 0	$ 20