Noncontrolling Interests (Preferred Stockholders' Equity in Subsidiaries) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Noncontrolling Interest [Line Items]
Subsidiary Capital Stock Combined Voting Power Preferred	25.00%
Subsidiary Capital Stock Combined Voting Power Common Stock	75.00%
Redeemable Preferred Stock Member
Noncontrolling Interest [Line Items]
Preferred stock-perpetual voting variable term shares issued	300,000
Preferred stock-perpetual voting, total issuance dollar value	$ 300
Preferred stock-perpetual voting, dividend rate	6.125%
Preferred stock-perpetual voting, cumulative dividend period	7 years
Preferred stock-perpetual voting, dividend increase percentage each interval once shares become callable	50.00%
Preferred stock-perpetual voting, dividend increase interval once shares become callable	6 months