Fair Value of Financial Investments (Details Textual) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Fair Value of Financial Investments and Liabilities (Textual) [Abstract]
Aggregate carrying value of remaining private equity funds	$ 72,000,000
Estimated market value of long-term and short-term debt	4,600,000,000	4,000,000,000
Aggregate carrying value of long-term and short-term debt	$ 4,400,000,000	$ 4,000,000,000