Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Parent Company [Member]
Cash flows from operating activities:
Consolidated net income	$ 50,820	$ 43,416
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	(121,361)	(130,082)
(Gain) Loss on sale of depreciable real estate assets excluded from discontinued operations	0	73
Gain on sale of non-depreciable real estate assets	(150)	0
Stock compensation expense	4,024	3,018
Amortization of debt premium	(1,569)	(3,147)
Proceeds from Other Operating Activities	(21,782)	(40,669)
Net cash provided by operating activities	152,704	132,773
Cash flows from investing activities:
Purchases of real estate and other assets	0	(62,817)
Normal capital improvements	(51,775)	(86,338)
Contributions to Real Estate Joint Ventures	(750)	0
Proceeds from disposition of real estate assets	5,860	0
Net cash (used in) provided by investing activities	(46,665)	(149,155)
Cash flows from financing activities:
Proceeds from Lines of Credit	150,000	155,000
Repayments of Lines of Credit	(110,000)	(75,000)
Principal payments on notes payable	(41,042)	(18,871)
Repurchase of common stock	(2,912)	(4,734)
Payment for Debt Extinguishment or Debt Prepayment Cost	(3)	(1)
Proceeds from issuances of common shares	199	67
Proceeds from Stock Options Exercised	625	0
Distributions to noncontrolling interests	(3,865)	(3,667)
Dividends paid on common shares	(104,876)	(98,791)
Dividends, Preferred Stock, Cash	(922)	(922)
Net cash used in financing activities	(112,796)	(46,919)
Net (decrease) increase in cash and cash equivalents	(6,757)	(63,301)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Beginning	88,867	121,800
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Ending	82,110	58,499
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	59,706	33,959
Restricted Cash	22,404	24,540
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Ending	82,110	58,499
Supplemental disclosure of cash flow information:
Interest paid	24,889	24,785
Income Taxes Paid	2,522	10
Supplemental disclosure of noncash investing and financing activities:
Conversion of units to shares of common stock	2,780	167
Accrued construction in progress	14,640	21,810
Interest capitalized	795	2,020
Marked To Market Adjustment On Derivative Instruments	(1,363)	6,743
Limited Partner [Member]
Cash flows from operating activities:
Consolidated net income	50,820	43,416
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	(121,361)	(130,082)
(Gain) Loss on sale of depreciable real estate assets excluded from discontinued operations	0	73
Gain on sale of non-depreciable real estate assets	(150)	0
Stock compensation expense	4,024	3,018
Amortization of debt premium	(1,569)	(3,147)
Proceeds from Other Operating Activities	(21,782)	(40,669)
Net cash provided by operating activities	152,704	132,773
Cash flows from investing activities:
Purchases of real estate and other assets	0	(62,817)
Normal capital improvements	(51,775)	(86,338)
Contributions to Real Estate Joint Ventures	(750)	0
Proceeds from disposition of real estate assets	5,860	0
Net cash (used in) provided by investing activities	(46,665)	(149,155)
Cash flows from financing activities:
Proceeds from Lines of Credit	150,000	155,000
Repayments of Lines of Credit	(110,000)	(75,000)
Principal payments on notes payable	(41,042)	(18,871)
Repurchase of common units	(2,912)	(4,734)
Payment for Debt Extinguishment or Debt Prepayment Cost	(3)	(1)
Proceeds from issuances of common units	199	67
Proceeds from Stock Options Exercised	625	0
Distributions paid on common units	(108,741)	(102,458)
Dividends, Preferred Stock, Cash	(922)	(922)
Net cash used in financing activities	(112,796)	(46,919)
Net (decrease) increase in cash and cash equivalents	(6,757)	(63,301)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Beginning	88,867	121,800
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Ending	82,110	58,499
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	59,706	33,959
Restricted Cash	22,404	24,540
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Ending	82,110	58,499
Supplemental disclosure of cash flow information:
Interest paid	24,889	24,785
Income Taxes Paid	2,522	10
Supplemental disclosure of noncash investing and financing activities:
Accrued construction in progress	14,640	21,810
Interest capitalized	795	2,020
Marked To Market Adjustment On Derivative Instruments	$ (1,363)	$ 6,743