Mortgage Loans on Real Estate (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) loans portfolio_segment	Sep. 30, 2014 loans	Sep. 30, 2015 USD ($) loans portfolio_segment	Sep. 30, 2014 loans	Dec. 31, 2014 USD ($)
Mortgage Loans on Real Estate [Abstract]
Mortgage loans on real estate	$ 2,452,402		$ 2,452,402		$ 2,434,580
Commitments outstanding	$ 64,300		$ 64,300
Number of portfolio segments that make up financing receivables | portfolio_segment	1		1
Number of mortgage loans satisfied by foreclosure | loans	0	1	0	6
Impaired mortgage loans, workout terms, interest only payments, six month terms			6 months
Impaired mortgage loans, workout terms, interest only payments, twelve month terms			12 months
Impaired mortgage loans, workout terms, cash flow sweep, number of months			12 months
Number of days past due, non-accrual status			90 days
Outstanding principal of loans in a non-accrual status	$ 16,000		$ 16,000		$ 6,000
Minimum [Member]
Mortgage Loans on Real Estate [Line Items]
Number of days past due, delinquent status			60 days