Fair Value Measurements Fair Value Measurements (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number Of Available For Sale Equity Securities Continuous Unrealized Loss Position	26
Fair Value, Level 1 to level 2 Transfers, Amount	$ 0
Preferred Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number Of Available For Sale Equity Securities Continuous Unrealized Loss Position	5
Available For Sale Equity Securities Continuous Unrealized Loss Position Fair Value	66,000,000
Available For Sale Equity Securities Continuous Unrealized Loss Position Aggregate Loss	7,000,000
Number Of Available For Sale Equity Securities Non Investment Grade Continuous Unrealized Loss Position Aggregate Loss	2
Available For Sale Equity Securities Non Investment Grade Continuous Unrealized Loss Position Fair Value	17,000,000
Available For Sale Equity Securities Non Investment Grade Continuous Unrealized Loss Position Aggregate Loss	4,000,000
Common Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number Of Available For Sale Equity Securities Continuous Unrealized Loss Position	5
Available For Sale Equity Securities Continuous Unrealized Loss Position Fair Value	47,000,000
Available For Sale Equity Securities Continuous Unrealized Loss Position Aggregate Loss	$ 700,000