Real Estate (Other Dispositions) (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) property	Dec. 31, 2017 USD ($) property	Dec. 31, 2016 USD ($)
Other Dispositions by Property Type
Income from sales of real estate	$ 24,500	$ 126,004	$ 92,049	$ 105,296
Total
Other Dispositions by Property Type
Proceeds		407,600	216,700	444,100
Income from sales of real estate		126,000	92,000	96,500
Operating Properties
Other Dispositions by Property Type
Proceeds		327,900	41,300	326,900
Income from sales of real estate		$ 81,000	4,500	75,400
Number of properties sold | property		10
Operating Properties, Noncontrolling Interest
Other Dispositions by Property Type
Income from sales of real estate		$ 9,800
Net Lease
Other Dispositions by Property Type
Proceeds		79,700	175,400	117,200
Income from sales of real estate		$ 45,000	$ 87,500	$ 21,100
Number of properties sold | property		5	1
Net Lease | Net Lease Asset
Other Dispositions by Property Type
Income from sales of real estate			$ 62,500
Noncontrolling interest at carrying value			3,500
Payments for repurchase of redeemable noncontrolling interest			$ 12,000