Shareholders' Equity (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net of tax unrealized gains (losses) related to credit-only impaired securities	$ 58		$ 54
Common Stock options issued under stock incentive plan, average exercise price	$ 56.44	$ 44.01
Compensation expense related to stock incentive plans	$ 7	$ 13
Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Common Stock, shares issued	102,330
Restricted Common Stock, fair value per share	$ 56.44
Common Stock options issued under stock incentive plan	1,000,000
Common Stock options issued under stock incentive plan, average exercise price	$ 56.44
Annual Equity Bonus Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other benefit plans, shares	84,036
Common Stock issued, fair value per share	$ 57.16