Consolidated Statements Of Shareholder's Equity And Comprehensive Income (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended					12 Months Ended
	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Preferred Series A [Member]	Dec. 31, 2010 Preferred Series A [Member]	Dec. 31, 2009 Preferred Series A [Member]	Dec. 31, 2011 Maximum [Member]	Dec. 31, 2009 Maximum [Member]
Unrealized loss (gain) on investments, tax	$ 1					$ 1	$ 1
Unrealized gain on derivative instruments, tax		1
Reclassification adjustment for gain realized on investments, tax	$ 1
Preferred stock, shares authorized			100,000	100,000	100,000
Preferred stock, par value
Preferred stock, stated value			$ 5,000	$ 5,000	$ 5,000
Preferred stock, shares issued			0	0	0
Preferred stock, shares outstanding			0	0	0