Leasing Activities (Schedule of Lease Receivables) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Lease Receivables [Line Items]
Recovery of Direct Costs	$ 198,200	$ 188,600	$ 193,700
2019	600,385
2020	586,609
2021	529,961
2022	463,462
2023	397,150
Thereafter	1,582,598
Operating Leases, Future Minimum Payments Receivable	$ 4,160,165