Shareholders' Equity (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended								3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Minimum [Member]	Dec. 31, 2013 Maximum [Member]	Dec. 31, 2013 Stock Options [Member]	Dec. 31, 2013 Restricted Stock [Member]	Dec. 31, 2013 Stock Incentive Plan [Member]	Mar. 31, 2013 Annual Equity Bonus Plan [Member]	Mar. 31, 2012 Annual Equity Bonus Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock reserved for issuance under stock incentive plans								11,700,000
Rate of options exercisable per year, commencing one year after grant	20% per year commencing one year after grant
Duration of options expiration, after date of grant	10 years
Total intrinsic value of options exercised	$ 35	$ 25	$ 23
Cash received from the exercise of stock options	44	40	33
Tax benefit related to exercise of stock options	11	8	7
Restricted Common Stock vesting period				3 years	4 years
Other benefit plans, shares									88,602	111,270
Common Stock issued, fair value per share									$ 47.12	$ 38.38
Total compensation expense related to stock incentive plans	36	26	22
Tax benefit related to compensation costs	12	8	7
Unrecognized compensation expense related to equity-based awards that have yet to vest						27	12
Weighted average period of cost expected to be recognized						3 years 3 months 18 days	2 years 4 months 24 days
Net of tax unrealized gains (losses) related to credit-only impaired securities	$ 54	$ 33	$ (16)