Accounting Policies (Impairment & Other) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) segment	Dec. 31, 2014 USD ($) segment	Dec. 31, 2013 USD ($) segment
Deferred Financing Costs
Amortized costs included in interest expense	$ 18,700	$ 16,900	$ 13,500
Revenue Recognition
Straight-line rent receivables	219,064	187,572
Allowance for straight-line rent receivable	$ 101,400	$ 83,500
Term of resident lease agreements, minimum (in months)	12 months
Term of resident lease agreements, maximum (in months)	18 months
Notice period to cancel lease agreements by the resident (in days)	30 days
Segment Reporting [Abstract]
Number of reportable segments | segment	3	3	3