Shareholders' Equity (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 Y	Mar. 31, 2011	Dec. 31, 2011
Stockholders' Equity (Textual) [Abstract]
Expected dividend yield	1.80%
Expected volatility	39.00%
Expected term (in years)	7.3
Risk-free rate	1.40%
Restricted Common Stock, shares issued	131,731
Restricted Common Stock, fair value per share	$ 38.11
Fair value per share of options granted	$ 13.03
Total compensation expense related to stock incentive plans	$ 6	$ 5
Net of tax unrealized gains (losses) related to credit-only impaired securities	$ (8)		$ (15)
Stock incentive plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock options issued under stock incentive plan	1,100,000
Common Stock options issued under stock incentive plan, average exercise price	$ 38.11
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
Voting Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, shares authorized	12,500,000
Preferred Stock, par value	$ 0
Nonvoting Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, shares authorized	12,500,000
Preferred Stock, par value	$ 0