Shareholders' Equity (Details Textuals) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended					9 Months Ended	3 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 Securities CollateralizedLoanObligations Year	Sep. 30, 2010	Dec. 31, 2010	Sep. 30, 2011 Voting Preferred Stock [Member]	Sep. 30, 2011 Nonvoting Preferred Stock [Member]	Sep. 30, 2011 Stock incentive plan [Member]	Mar. 31, 2011 Annual Co-CEO Equity Bonus Plan [Member]
Class of Stock [Line Items]
Preferred Stock, shares authorized						12,500,000	12,500,000
Preferred Stock, par value
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other benefit plans, shares									188,302
Common Stock options issued under stock incentive plan, average exercise price								$ 34.34
Common Stock options issued under stock incentive plan								1,100,000
Common Stock issued, fair value per share									$ 33.99
Stockholders' Equity (Textuals) [Abstract]
Pretax unrealized gains (losses) related to credit-only impaired securities	$ 14		$ 14		$ 17
Net of tax unrealized gains (losses) related to credit-only impaired securities	9		9		11
Restricted Common Stock, shares issued			131,955
Restricted Common Stock, fair value per share			$ 34.34
Fair value per share of options granted			$ 12.49
Expected dividend yield			1.90%
Expected volatility			38.00%
Expected term			7.3
Risk-free rate			3.04%
Total share based compensation	$ 5	$ 5	$ 16	$ 15