Shareholders' Equity Schedule of Net Income from Participating Securities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Equity [Abstract]
Net income from participating securities	$ 2	$ 3	$ 7	$ 8

Aggregate of earnings distributed and earnings allocated to participating securities under the two-class method to the extent that participating securities may share in earnings as if all of the earnings for the period had been distributed.

No definition available.

Name:	us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarnings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration