Common and Preferred Stock (Restricted Stock, Performance Share Awards and Options Activity) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	3 years
Activity [Roll Forward]
Nonvested balance at beginning of year (in shares)	1,154,590
Granted (in shares)	452,488
Vested (in shares)	(521,882)
Forfeited (in shares)	(52,908)
Nonvested balance at end of year (in shares)	1,032,288	1,154,590
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Nonvested balance at beginning of year, weighted-average grant date fair value (in dollars per share)	$ 50.40
Granted, weighted-average grant date fair value (in dollars per share)	$ 54.77	$ 46.72	$ 51.50
Vested, weighted-average grant date fair value (in dollars per share)	$ 53.22
Forfeited, weighted-average grant date fair value (in dollars per share)	$ 51.34
Nonvested balance at end of year, weighted-average grant date fair value (in dollars per share)	$ 50.84	$ 50.40
Performance Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	3 years
Activity [Roll Forward]
Nonvested balance at beginning of year (in shares)	1,318,398
Granted (in shares)	566,386
Vested (in shares)	(448,416)
Forfeited (in shares)	(85,294)
Nonvested balance at end of year (in shares)	1,351,074	1,318,398
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Nonvested balance at beginning of year, weighted-average grant date fair value (in dollars per share)	$ 45.96
Granted, weighted-average grant date fair value (in dollars per share)	$ 50.13	$ 42.95	$ 42.66
Vested, weighted-average grant date fair value (in dollars per share)	$ 58.42
Forfeited, weighted-average grant date fair value (in dollars per share)	$ 43.34
Nonvested balance at end of year, weighted-average grant date fair value (in dollars per share)	$ 43.72	$ 45.96
Restricted Stock and Performance Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Total fair value of awards vested	$ 53	$ 47	$ 46
Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	3 years
Maximum term (in years)	10 years
Option activity [Roll Forward]
Shares underlying options - Balance at beginning of year (in shares)	5,036,652
Shares underlying options - Granted (in shares)	536,302
Shares underlying options - Exercised (in shares)	(1,065,939)
Shares underlying options - Forfeited (in shares)	(102,451)
Shares underlying options - Expired (in shares)	(18,699)
Shares underlying options - Balance at end of year (in shares)	4,385,865	5,036,652
Shares underlying options - Exercisable (in shares)	3,348,329
Additional disclosures pertaining to options [Abstract]
Balance at beginning of year, weighted average exercise price (in dollars per share)	$ 38.69
Granted, weighted average exercise price (in dollars per share)	$ 54.59
Exercised, weighted average exercise price (in dollars per share)	$ 29.14
Forfeited, weighted average exercise price (in dollars per share)	$ 50.49
Expired, weighted average exercise price (in dollars per share)	$ 47.42
Balance at end of year, weighted average exercise price (in dollars per share)	$ 42.64	$ 38.69
Exercisable at end of year, weighted average exercise price (in dollars per share)	$ 40.15
Balance at end of year, weighted average remaining contractual term (years)	4.7
Balance at end of year, aggregate intrinsic value	81
Exercisable at end of year, weighted average remaining contractual term (years)	3.6
Exercisable at end of year, aggregate intrinsic value	71
Granted, weighted average grant date fair value (in dollars per share)	$ 7.78	$ 6.22	$ 6.79
Total intrinsic value of stock options exercised	29	32	9
Cash received from option exercises	31	41	10
Tax benefit realized from options exercised	$ 11	$ 12	$ 3