Common Shareholders' Equity (Assumptions and Options) (Details) (Options [Member], USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
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
Assumptions used to estimate the fair value of options using the Black-Scholes option pricing model [Abstract]
Expected volatility (in hundredths)			21.00%	[1]	21.54%	[1]
Expected volatility, low range (in hundredths)	20.08%	[1]
Expected volatility, high range (in hundredths)	20.15%	[1]
Expected dividends (in hundredths)			3.99%		4.03%
Expected dividends, low range (in hundredths)	3.28%
Expected dividends, high range (in hundredths)	3.64%
Expected term (years)	7 years	[2]	6 years 8 months 12 days	[2]	6 years	[2]
Risk-free rate (in hundredths)			1.37%		2.80%
Risk-free rate, low range (in hundredths)	1.15%
Risk-free rate, high range (in hundredths)	1.40%
Option activity [Roll Forward]
Shares underlying options - Balance at beginning of year (in shares)	3,191,090
Shares underlying options - Granted (in shares)	393,396
Shares underlying options - Exercised (in shares)	(363,279)
Shares underlying options - Forfeited (in shares)	(28,860)
Shares underlying options - Expired (in shares)	(800)
Shares underlying options - Exercisable (in shares)	2,453,246
Shares underlying options - Balance at end of year (in shares)	3,191,547		3,191,090
Additional disclosures pertaining to options [Abstract]
Balance at beginning of year, weighted average exercise price (in dollars per share)	$ 50.69
Granted, weighted average exercise price (in dollars per share)	$ 72.63
Exercised, weighted average exercise price (in dollars per share)	$ 38.19
Forfeited, weighted average exercise price (in dollars per share)	$ 64.46
Expired, weighted average exercise price (in dollars per share)	$ 28.38
Balance at end of year, weighted average exercise price (in dollars per share)	$ 54.70		$ 50.69
Exercisable at end of year, weighted average exercise price (in dollars per share)	$ 51.78
Balance at end of year, weighted average remaining contractual term (years)	5 years 10 months 24 days
Balance at end of year, aggregate intrinsic value	$ 99
Exercisable at end of year, weighted average remaining contractual term (years)	5 years 1 month 6 days
Exercisable at end of year, aggregate intrinsic value	83
Granted, weighted average grant date fair value (in dollars per share)	$ 9.20		$ 7.69		$ 7.78
Total intrinsic value of stock options exercised	14		57		29
Cash received from option exercises	14		55		31
Tax benefit realized from options exercised	$ 5		$ 22		$ 11

[1] Based on historical experience.

[2] Based on historical exercise and post-vesting cancellation experience adjusted for outstanding awards.