Shareholders' Equity (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	9 Months Ended				9 Months Ended	3 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Jun. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Stock incentive plan [Member]	Mar. 31, 2012 Annual Co-CEO Equity Bonus Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other benefit plans, shares							111,270
Common Stock issued, fair value per share							$ 38.38
Common Stock options issued under stock incentive plan						1,100,000
Common Stock options issued under stock incentive plan, average exercise price						$ 38.10
Total compensation expense related to stock incentive plans	$ 5	$ 20	$ 16
Stockholders' Equity (Textual) [Abstract]
Expected dividend yield		1.80%
Expected volatility		39.00%
Expected term (in years)		7 years 3 months 18 days
Risk-free rate		1.40%
Restricted Common Stock, shares issued		133,931
Restricted Common Stock, fair value per share		$ 38.10
Fair value per share of options granted		$ 13.02
Net of tax unrealized gains (losses) related to credit-only impaired securities	$ 23	$ 23		$ (1)	$ (16)