Equity and Mezzanine Securities, Narrative (Details) - USD ($)						1 Months Ended					3 Months Ended				9 Months Ended		12 Months Ended
	Oct. 16, 2017	Oct. 02, 2017	Jun. 09, 2016	Mar. 30, 2016	Jun. 17, 2015	Sep. 30, 2017	Jun. 30, 2017	May 31, 2017	Sep. 30, 2016	Jun. 30, 2015	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Mar. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Nov. 30, 2004
Class of Stock [Line Items]
Shares Issued, Weighted Average Price Per Share							$ 85.01					$ 85.01	$ 76,470
Aggregate Value of Shares to be Issued in Accordance to Sales Agreement										$ 225,000,000					$ 450,000,000.0
Commission, Maximum Percentage of Gross Sales Price Per Share According to Sales Agreement															2.00%
New shares issued (in shares)				6,037,500				4,830,000	3,737,500			400,000,000	280,502,000	6,037,500
Shares Issued, Price Per Share								$ 86.00	$ 76.50							$ 76.50
Proceeds from Issuance of Common Stock				$ 385,400,000				$ 408,900,000	$ 283,600,000					$ 385,400,000
Redemption price (in dollars per share)						$ 25.00					$ 25.00				$ 25.00
Share Price				$ 66.50										$ 66.50
Total consideration transferred						$ 26,400,000					$ 2,000,000				$ 92,752,000		$ 89,700,000
Series A-4 Preferred Stock
Class of Stock [Line Items]
Preferred Stock, Dividends Per Share, Declared											$ 0.40625
Stock Redeemed or Called During Period, Shares											438,448
Series A-4 Preferred Stock | Subsequent Event
Class of Stock [Line Items]
Payments of dividends		$ 1,514
Common Stock
Class of Stock [Line Items]
Dividends per common share											$ 0.67
Common Stock | Subsequent Event
Class of Stock [Line Items]
Payments of dividends	$ 55,006
Common OP Units
Class of Stock [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares					250,000,000.0	298,900	23,311
Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividends Per Share, Declared											$ 0.4453125
Preferred Stock [Member] | Subsequent Event
Class of Stock [Line Items]
Payments of dividends	$ 441
Series A-4 preferred OP units
Class of Stock [Line Items]
Stock Redeemed or Called During Period, Shares											200,000
Common Stock
Class of Stock [Line Items]
Authorized to be repurchased (in shares)																		1,000,000
Remaining number of shares authorized to be repurchased (in shares)						400,000					400,000				400,000
Series A-4 preferred OP units
Class of Stock [Line Items]
Conversion of Common OP Units to common stock (in shares)															9,000,000	12,389,000
Series A-4 preferred OP units | Common OP Units
Class of Stock [Line Items]
Conversion of Common OP Units to common stock (in shares)															3,996,000	5,505,000
Conversion of Common OP Units
Class of Stock [Line Items]
Conversion of Common OP Units to common stock (in shares)															25,238	24,896
Conversion of Common OP Units | Common OP Units
Class of Stock [Line Items]
Conversion of Common OP Units to common stock (in shares)															25,238
Series A-1 Preferred OP Units
Class of Stock [Line Items]
Conversion of Common OP Units to common stock (in shares)															18,319,000	11,490,000
Series A-1 Preferred OP Units | Common OP Units
Class of Stock [Line Items]
Conversion of Common OP Units to common stock (in shares)															44,676,000	28,021,000
Carefree Communities
Class of Stock [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares			3,329,880
Business Acquisition, Share Price			$ 67.57
Total consideration transferred			$ 1,684,140,000
Green Courte [Member] | Series A-4 Preferred Stock and OP Units [Member]
Class of Stock [Line Items]
Stock Redeemed or Called During Period, Value											$ 24,700,000