Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2016
Other expense (income) [Abstract]
Provision for impairment	$ 1,700
Equity in income of investments in real estate partnerships (note 4)	56,518	$ 22,508	$ 31,270
Discontinued operations, net (note 3):
Gain (Loss) on Sale of Properties, Net of Applicable Income Taxes	47,321	35,606	55,077
Net income	166,992	152,543	188,847
Parent Company [Member]
Revenues:
Minimum rent	444,305	415,155	390,697
Percentage rent	4,128	3,750	3,488
Recoveries from tenants and other income	140,611	125,295	119,618
Total revenues	614,371	569,763	537,898
Management Fees Revenue	25,327	25,563	24,095
Operating expenses:
Depreciation and amortization	162,327	146,829	147,791
Operating and maintenance	95,022	82,978	77,788
General and administrative	65,327	65,600	60,242
Real estate taxes	66,395	61,855	59,031
Other operating expenses	14,081	7,836	8,496
Total operating expenses	403,152	365,098	353,348
Other expense (income) [Abstract]
Interest Expense	90,712	102,622	109,491
Provision for impairment	4,200	0	1,257
Early extinguishment of debt	14,240	8,239	18
Net investment income, including unrealized (gains) losses of ($773), $1,734, and $1,058 in 2016, 2015, and 2014, respectively (notes 11)	1,672	625	9,449
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain	0	0	(18,271)
Gain (Loss) on Derivative Instruments, Net, Pretax	40,586	0	0
Nonoperating Income (Expense)	(148,066)	(110,236)	(83,046)
Income from operations before equity in income of investments in real estate partnerships	63,153	94,429	101,504
Equity in income of investments in real estate partnerships (note 4)	56,518	22,508	31,270
Federal Income Tax Expense (Benefit), Continuing Operations	0	0	(996)
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	119,671	116,937	133,770
Discontinued operations, net (note 3):
Gain (Loss) on Sale of Properties, Net of Applicable Income Taxes	47,321	35,606	55,077
Net income	166,992	152,543	188,847
Noncontrolling interests:
Noncontrolling Interest in Net Income (Loss) Operating Partnerships, Nonredeemable	(257)	(240)	(319)
Noncontrolling Interest in Net Income (Loss) Limited Partnerships, Nonredeemable	(1,813)	(2,247)	(1,138)
Income attributable to noncontrolling interests	(2,070)	(2,487)	(1,457)
Net income attributable to the Company	164,922	150,056	187,390
Preferred stock dividends	(21,062)	(21,062)	(21,062)
Net Income (Loss) Available to Common Stockholders, Basic	$ 143,860	$ 128,994	$ 166,328
Continuing operations (in dollars per share)	$ 1.43	$ 1.37	$ 1.80
Continuing operations (in dollars per share)	$ 1.42	$ 1.36	$ 1.80
Partnership Interest [Member]
Revenues:
Minimum rent	$ 444,305	$ 415,155	$ 390,697
Percentage rent	4,128	3,750	3,488
Recoveries from tenants and other income	140,611	125,295	119,618
Total revenues	614,371	569,763	537,898
Management Fees Revenue	25,327	25,563	24,095
Operating expenses:
Depreciation and amortization	162,327	146,829	147,791
Operating and maintenance	95,022	82,978	77,788
General and administrative	65,327	65,600	60,242
Real estate taxes	66,395	61,855	59,031
Other operating expenses	14,081	7,836	8,496
Total operating expenses	403,152	365,098	353,348
Other expense (income) [Abstract]
Interest Expense	90,712	102,622	109,491
Provision for impairment	4,200	0	1,257
Early extinguishment of debt	14,240	8,239	18
Net investment income, including unrealized (gains) losses of ($773), $1,734, and $1,058 in 2016, 2015, and 2014, respectively (notes 11)	1,672	625	9,449
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain	0	0	(18,271)
Gain (Loss) on Derivative Instruments, Net, Pretax	40,586	0	0
Nonoperating Income (Expense)	(148,066)	(110,236)	(83,046)
Income from operations before equity in income of investments in real estate partnerships	63,153	94,429	101,504
Equity in income of investments in real estate partnerships (note 4)	56,518	22,508	31,270
Federal Income Tax Expense (Benefit), Continuing Operations	0	0	(996)
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	119,671	116,937	133,770
Discontinued operations, net (note 3):
Gain (Loss) on Sale of Properties, Net of Applicable Income Taxes	47,321	35,606	55,077
Net income	166,992	152,543	188,847
Noncontrolling interests:
Noncontrolling Interest in Net Income (Loss) Limited Partnerships, Nonredeemable	(1,813)	(2,247)	(1,138)
Income attributable to noncontrolling interests	(1,813)	(2,247)	(1,138)
Net income attributable to the Company	165,179	150,296	187,709
Preferred unit distributions	(21,062)	(21,062)	(21,062)
Net (loss) income attributable to common unit holders	$ 144,117	$ 129,234	$ 166,647
Continuing operations (in dollars per share)	$ 1.43	$ 1.37	$ 1.80
Continuing operations (in dollars per share)	1.43	1.37	1.80
Continuing operations (in dollars per share)	1.42	1.36	1.80
Continuing operations (in dollars per share)	$ 1.42	$ 1.36	$ 1.80