Subsequent Events (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended	1 Months Ended	3 Months Ended	1 Months Ended	9 Months Ended	1 Months Ended
	Apr. 30, 2012 Quarterly [Member]	Mar. 31, 2012 Quarterly [Member]	Apr. 30, 2012 Annual [Member]	Mar. 31, 2012 Annual [Member]	Oct. 23, 2012 Subsequent Event [Member] Repurchase of Equity [Member]	Sep. 30, 2012 Subsequent Event [Member] Repurchase of Equity [Member]	Oct. 23, 2012 Subsequent Event [Member] Dividend Declared [Member]
Subsequent Event [Line Items]
Subsequent event, date					Oct. 18, 2012		Oct. 17, 2012
Subsequent event, description					Increase to existing share repurchase authorization.		Common Stock cash dividend declared for the period from August 1, 2012 to October 31, 2012 to be paid on November 8, 2012 to holders of record as of October 29, 2012.
Subsequent event, amount							$ 12
Common stock, dividends, per share, declared	$ 0.075	$ 0.06	$ 0.30	$ 0.24			$ 0.075
Stock repurchase program, remaining authorized repurchase amount					$ 400	$ 136