Reportable Segments- Consolidated Net Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Operations revenues	$ 206,564	$ 197,007	$ 609,605	$ 573,973
Operations expenses	(106,755)	(102,437)	(305,412)	(288,509)
Income from segment operations	99,809	94,570	304,193	285,464
Interest income	1,729	1,881	5,240	5,605
Depreciation on real estate assets and rental homes	(28,410)	(27,831)	(84,861)	(83,234)
Amortization of in-place leases	(616)	(1,075)	(1,950)	(3,791)
Income (loss) from operations	72,512	67,545	222,622	204,044
Reconciliation to Consolidated net income:
Corporate interest income	29	21	74	872
Income from other investments, net	1,822	1,869	5,119	6,098
General and administrative	(7,225)	(7,623)	(22,172)	(20,178)
Property rights initiatives and other	(687)	(751)	(1,934)	(2,063)
Early debt retirement	0	(5,087)	(16,922)	(5,087)
Interest and related amortization	(26,227)	(27,864)	(79,648)	(84,177)
Equity in income of unconsolidated joint ventures	1,882	1,237	3,606	3,768
Gain (Loss) on Condemnation	0	929	0	929
Consolidated net income	42,106	30,276	110,745	104,206
Total assets	3,443,390	3,451,148	3,443,390	3,451,148	$ 3,446,339
Capital improvements			67,838	41,645
Property Operations
Segment Reporting Information [Line Items]
Operations revenues	194,983	184,270	573,797	541,415
Operations expenses	(96,152)	(91,939)	(274,109)	(261,744)
Income from segment operations	98,831	92,331	299,688	279,671
Interest income	692	696	2,114	2,266
Depreciation on real estate assets and rental homes	(25,703)	(25,010)	(76,668)	(74,815)
Amortization of in-place leases	(616)	(1,075)	(1,950)	(3,791)
Income (loss) from operations	73,204	66,942	223,184	203,331
Reconciliation to Consolidated net income:
Total assets	3,193,473	3,170,718	3,193,473	3,170,718
Capital improvements			37,211	22,111
Home Sales and Rentals Operations
Segment Reporting Information [Line Items]
Operations revenues	11,581	12,737	35,808	32,558
Operations expenses	(10,603)	(10,498)	(31,303)	(26,765)
Income from segment operations	978	2,239	4,505	5,793
Interest income	1,037	1,185	3,126	3,339
Depreciation on real estate assets and rental homes	(2,707)	(2,821)	(8,193)	(8,419)
Amortization of in-place leases	0	0	0	0
Income (loss) from operations	(692)	603	(562)	713
Reconciliation to Consolidated net income:
Total assets	$ 249,917	$ 280,430	249,917	280,430
Capital improvements			$ 30,627	$ 19,534