Investments - Equity Method LLCs (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investments Disclosures [Abstract]
Available-for-sale-Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Securities that have had Recognized Credit Losses in Earnings, Aggregate Losses	$ 0	$ (300,000)
Equity Method Investment, Summarized Financial Information, Assets	3,392,100,000	3,643,600,000
Equity Method Investment, Summarized Financial Information, Liabilities	576,300,000	421,000,000
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	181,100,000	134,600,000	(13,800,000)
Equity Method Limited Liability Investments at Cost Plus Cumulative Undistributed Earnings	245,100,000	253,000,000
Outstanding Commitments to Fund Equity Method Limited Liability Investments	$ 50,400,000