Estimated Fair Values (Narrative) (Details) (USD $)	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Optional Advance Commitments Excluding Commitments to Fund CIP and EDP Advances	$ 50,000,000
Other Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Option, Ineligible Items, Aggregate Carrying Amount	$ 25,085,000