Leasing Activities (Schedule of Lease Receivables) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Lease Receivables [Line Items]
Operating Leases, Future Minimum Payments Receivable, Current	$ 597,811
Operating Leases, Future Minimum Payments Receivable, in Two Years	585,202
Operating Leases, Future Minimum Payments Receivable, in Three Years	525,966
Operating Leases, Future Minimum Payments Receivable, in Four Years	463,653
Operating Leases, Future Minimum Payments Receivable, in Five Years	404,912
Operating Leases, Future Minimum Payments Receivable, Thereafter	1,717,524
Operating Leases, Future Minimum Payments Receivable	4,295,068
Tenant Reimbursements	$ 193,400	$ 201,800	$ 196,300