Business and Summary of Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013 customers	Dec. 31, 2012	Dec. 31, 2011
Dividends Paid [Line Items]
Concentration of credit risk, revenues from four customers	55.00%
Number of customers, concentration of credit risk	4
Labor costs capitalized	$ 44,100,000	$ 41,600,000	$ 35,600,000
Interest costs capitalized	1,800,000	1,900,000	2,100,000
Estimated useful life of respective assets	20 years
Distributions	(434,687,000)	(355,574,000)	(137,765,000)
Cash distribution per share	$ 1.10	$ 0.90	$ 0.35
Straight line revenue	147,700,000	165,800,000	144,000,000
Straight-line ground rent expense	29,700,000	33,700,000	31,000,000
Employers percentage of employees first 6 percent	75.00%	50.00%
Company's contribution	6,000,000	4,400,000	2,900,000
Employee maximum annual contribution eligible for match	6.00%	6.00%
Dividends Declared and Paid [Member]
Dividends Paid [Line Items]
Distributions	$ (434,500,000)	$ (355,600,000)