Unsecured Senior Notes Unsecured Senior Notes (Narrative) (Details)	12 Months Ended
	Dec. 31, 2015
Debt Instrument [Line Items]
Maximum Secured Debt Leverage Ratio	55.00%
Senior Notes [Member]
Debt Instrument [Line Items]
Maximum Leverage Ratio	60.00%
Maximum Secured Debt Leverage Ratio	50.00%
Minimum Interest Coverage Ratio	1.50
Minimum Unencumbered Asset Value Percentage Of Unsecured Debt	150.00%