Preferred Stock Preferred Stock (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Class of Stock [Line Items]
Number Of Full Quarterly Dividend Payments In Default Before Preferred Stockholders Elect Board Of Directors	4
Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Outstanding	407,000	407,000
Preferred Stock, Value, Outstanding	$ 41	$ 41
Dividends Payable	1	1
Preferred Stock Class, Serial Preferred [Member]
Class of Stock [Line Items]
Preferred Stock, Stated Value Per Share	$ 100	$ 100
Preferred Stock, Shares Authorized	3,500,000	3,500,000
Preferred Stock Class, 5% Preferred [Member]
Class of Stock [Line Items]
Preferred Stock, Stated Value Per Share	$ 100	$ 100
Preferred Stock, Shares Authorized	127,000	127,000
Preferred Stock, Dividend Rate, Percentage	5.00%	5.00%
Preferred Stock, Redemption Price Per Share	$ 110.0	$ 110.0
Preferred Stock Class, 5% Preferred [Member] | Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Outstanding	126,000	126,000
Preferred Stock, Value, Outstanding	13	13
Preferred Stock Class, No Par Serial Preferred [Member]
Class of Stock [Line Items]
Preferred Stock, No Par Serial Preferred, Shares Authorized	16,000,000	16,000,000
Preferred Stock, No Par Serial Preferred Stock, Shares Issued	0	0
Preferred Stock, No Par Serial Preferred, Shares Outstanding	0	0
4.52% to 4.72% Serial Preferred Stock [Member] | Preferred Stock Class, Serial Preferred [Member] | Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Outstanding	149,000	149,000
Preferred Stock, Value, Outstanding	15	15
5.00% to 5.40% Serial Preferred Stock [Member] | Preferred Stock Class, Serial Preferred [Member] | Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Outstanding	108,000	108,000
Preferred Stock, Value, Outstanding	10	10
6.00% Serial Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage	6.00%	6.00%
6.00% Serial Preferred Stock [Member] | Preferred Stock Class, Serial Preferred [Member] | Nonredeemable Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Outstanding	6,000	6,000
Preferred Stock, Value, Outstanding	1	1
7.00% Serial Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage	7.00%	7.00%
7.00% Serial Preferred Stock [Member] | Preferred Stock Class, Serial Preferred [Member] | Nonredeemable Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Outstanding	18,000	18,000
Preferred Stock, Value, Outstanding	$ 2	$ 2
Minimum [Member] | 4.52% to 4.72% Serial Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage	4.52%	4.52%
Preferred Stock, Redemption Price Per Share	$ 102.3	$ 102.3
Minimum [Member] | 5.00% to 5.40% Serial Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage	5.00%	5.00%
Preferred Stock, Redemption Price Per Share	$ 100.0	$ 100.0
Maximum [Member] | 4.52% to 4.72% Serial Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage	4.72%	4.72%
Preferred Stock, Redemption Price Per Share	$ 103.5	$ 103.5
Maximum [Member] | 5.00% to 5.40% Serial Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage	5.40%	5.40%
Preferred Stock, Redemption Price Per Share	$ 101.0	$ 101.0