Derivative Instruments (Narrative) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Derivative, Notional Amount	$ 797,030,000	$ 740,332,000
Real Estate And Building Materials [Member]
Derivative [Line Items]
Derivative loss from industry concentration	3,700,000
Retirement communities [Member]
Derivative [Line Items]
Derivative loss from industry concentration	1,200,000
Manufacturing [Member]
Derivative [Line Items]
Derivative loss from industry concentration	1,200,000
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 641,700,000