Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Summary information for the reportable segments
Total revenues	$ 229,827	$ 242,481	$ 684,262	$ 740,388
Other operating expenses not allocated to segments	113,770	117,273	331,664	358,124
Total operating expenses	191,200	195,527	564,117	590,696
Proportionate property net operating income	38,627	46,954	120,145	149,692
Other items included in income before income tax benefit (expense)	(37,753)	583,169	243,174	544,454
Income before income tax benefit (expense)	874	630,123	363,319	694,146
Real Estate [Member]
Summary information for the reportable segments
Total revenues	229,827	234,048	684,262	690,571
Property operating expenses	77,430	78,254	232,453	232,572
Segment Reconciling Items [Member]
Summary information for the reportable segments
Total revenues	8,832	8,335	25,715	24,103
Total operating expenses	8,234	7,826	24,025	22,551
Proportionate property net operating income	598	509	1,690	1,552
Income before income tax benefit (expense)	598	509	1,690	1,552
Segment Reconciling Items [Member] | Real Estate [Member]
Summary information for the reportable segments
Property operating expenses	8,234	7,826	24,025	22,551
Corporate Non-Segment [Member]
Summary information for the reportable segments
Total revenues	3	21,739	8,573	103,761
Other operating expenses not allocated to segments	113,770	117,273	331,664	358,124
Total operating expenses	118,811	127,230	354,098	391,647
Proportionate property net operating income	(118,808)	(105,491)	(345,525)	(287,886)
Other items included in income before income tax benefit (expense)	(37,753)	583,169	243,174	544,454
Income before income tax benefit (expense)	(156,561)	477,678	(102,351)	256,568
Corporate Non-Segment [Member] | Real Estate [Member]
Summary information for the reportable segments
Property operating expenses	5,041	9,957	22,434	33,523
Same Store [Member] | Operating Segments [Member]
Summary information for the reportable segments
Total revenues	179,056	172,426	529,550	509,357
Total operating expenses	48,220	46,751	142,124	139,417
Proportionate property net operating income	130,836	125,675	387,426	369,940
Income before income tax benefit (expense)	130,836	125,675	387,426	369,940
Same Store [Member] | Operating Segments [Member] | Real Estate [Member]
Summary information for the reportable segments
Property operating expenses	48,220	46,751	142,124	139,417
Redevelopment and Development [Member] | Operating Segments [Member]
Summary information for the reportable segments
Total revenues	17,891	19,876	57,408	56,436
Total operating expenses	7,469	7,242	21,786	20,678
Proportionate property net operating income	10,422	12,634	35,622	35,758
Income before income tax benefit (expense)	10,422	12,634	35,622	35,758
Redevelopment and Development [Member] | Operating Segments [Member] | Real Estate [Member]
Summary information for the reportable segments
Property operating expenses	7,469	7,242	21,786	20,678
Acquisition [Member] | Operating Segments [Member]
Summary information for the reportable segments
Total revenues	10,656	10,630	30,886	18,567
Total operating expenses	3,317	2,826	9,144	5,224
Proportionate property net operating income	7,339	7,804	21,742	13,343
Income before income tax benefit (expense)	7,339	7,804	21,742	13,343
Acquisition [Member] | Operating Segments [Member] | Real Estate [Member]
Summary information for the reportable segments
Property operating expenses	3,317	2,826	9,144	5,224
Other Real Estate [Member] | Operating Segments [Member]
Summary information for the reportable segments
Total revenues	13,389	9,475	32,130	28,164
Total operating expenses	5,149	3,652	12,940	11,179
Proportionate property net operating income	8,240	5,823	19,190	16,985
Income before income tax benefit (expense)	8,240	5,823	19,190	16,985
Other Real Estate [Member] | Operating Segments [Member] | Real Estate [Member]
Summary information for the reportable segments
Property operating expenses	$ 5,149	$ 3,652	$ 12,940	$ 11,179