Acquisitions and Dispositions Dispositions (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) entities	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) buildings entities	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Dispositions Disclosures [Line Items]
Number of Unconsolidated Joint Ventures in which Equity Interests Held | entities	1		1
Equity in earnings of unconsolidated companies	$ 51,933	$ 3,534	$ 56,682	$ 25,394
Proceeds from Sale of Real Estate Held-for-investment			$ 1,977,127	174,882
Total Properties Sold or Classified as Held for Sale | buildings			127
Promote income	20,007	24,087	$ 20,007	24,087
Income Tax Expense (Benefit), Continuing Operations, Discontinued Operations			19,700
Income Tax Expense (Benefit)	5,426	(157)	7,557	186
Discontinued Operation, Tax Effect of Discontinued Operation	11,613	$ 0	11,613	0
Financing Receivable, Net	$ 423,946		423,946		$ 25,460
Capital distributions from unconsolidated companies			111,557	$ 36,328
Continuing Operations [Member]
Dispositions Disclosures [Line Items]
Income Tax Expense (Benefit)			$ (8,000)
Medical Office Portfolio Sale [Member]
Dispositions Disclosures [Line Items]
Number of Unconsolidated Joint Ventures in which Equity Interests Held | entities	2		2
Equity in earnings of unconsolidated companies			$ 47,500
Proceeds from Sale of Real Estate Held-for-investment			$ 2,350,000
Total Properties Sold or Classified as Held for Sale | buildings			77
Gains (Losses) on Sales of Investment Real Estate			$ 1,140,000
Financing Receivable, Net	$ 400,000		$ 400,000
Debt Instrument, Interest Rate, Stated Percentage	4.00%		4.00%
Capital distributions from unconsolidated companies			$ 105,300