Fair Value of Financial Instruments (Estimated Fair Values Of Financial Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Liabilities
Total return swap	$ 7,600	$ 11,525
Liabilities, Fair Value Disclosure, Recurring	297,909	301,785
Level 2 [Member]
Liabilities
Liabilities, Fair Value Disclosure, Recurring	297,600	301,525
Secured Debt [Member] | Borrowings [Member]
Liabilities
Liabilities, Fair Value Disclosure, Recurring	140,000	140,000
Secured Debt [Member] | Borrowings [Member] | Level 2 [Member]
Liabilities
Liabilities, Fair Value Disclosure, Recurring	140,000	140,000
Unsecured Debt [Member] | Borrowings [Member]
Liabilities
Liabilities, Fair Value Disclosure, Recurring	150,000	150,000
Unsecured Debt [Member] | Borrowings [Member] | Level 2 [Member]
Liabilities
Liabilities, Fair Value Disclosure, Recurring	150,000	150,000
Equity Contract [Member]
Liabilities
Equity contracts	309	260
Investments [Member]
Assets
Investments	$ 3,487,837	$ 3,380,642