Shareholder's Equity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 08, 2015	Dec. 31, 1999
Stockholders Equity Note [Line Items]
Preferred Stock, Shares Outstanding	867,846
Common stock, shares outstanding	113,518,212	75,408,571
Common shares and operating partnership units outstanding	117,738,615	79,571,567
Treasury Stock, Shares, Acquired	22,067	11,914
Preferred Stock, Liquidation Preference, Value	$ 43,400,000
Noncontrolling Interest in Joint Ventures	$ 2,300,000
RepurchasePlan%CSoutstanding	5.30%
Shares, Outstanding				2,100,000
Preferred Stock, Liquidation Preference Per Share	$ 50.00
Preferred Stock, Redemption Date	Oct. 01, 2026
Preferred Stock, Redemption Price Per Share	$ 50.00
Preferred Stock, Dividend Rate, Percentage	8.50%
Preferred Stock, Dividend Rate, Per-Dollar-Amount	$ 4.25
Equity Option [Member]
Stockholders Equity Note [Line Items]
Common stock shares issued (shares)		7,342	270,459
Maximum
Stockholders Equity Note [Line Items]
Common stock authorized for repurchase plan (shares)	4,000,000.0				4,000,000.0
Period Covered from 1999 to 2011
Stockholders Equity Note [Line Items]
Common stock repurchased and retired (shares)	1,900,000
Common stock repurchased and retired, value	$ 42,000,000
Common stock repurchased and retired (dollars per share)	$ 22.54
Dividend And Distribution Reinvestment And Share Purchase Plan
Stockholders Equity Note [Line Items]
Common stock issued for shareholders to reinvest distributions (shares)	7,906	8,562	9,055
Dividend And Distribution Reinvestment And Share Purchase Plan | Minimum
Stockholders Equity Note [Line Items]
Optional cash investments in common shares	$ 250
Dividend And Distribution Reinvestment And Share Purchase Plan | Maximum
Stockholders Equity Note [Line Items]
Optional cash investments in common shares	$ 5,000
Common stock registered for Dividend and Distribution Reinvestment and Share Purchase Plan (shares)	9,600,000
Discount rate on sale of common stock (percent)	5.00%
Parent Company [Member]
Stockholders Equity Note [Line Items]
Preferred Stock, Shares Outstanding	867,846	0
Common stock, shares outstanding	113,518,212	75,408,571
Percentage of Operating Partnership net income (percent)	95.00%	94.80%	94.70%
Noncontrolling Interest in Joint Ventures	$ 2,306,000	$ 0
Common stock registered for Dividend and Distribution Reinvestment and Share Purchase Plan (shares)	145,000,000	100,000,000
Proceeds from issuance of common stock	$ 291,000	$ 622,000	$ 1,042,000
Proceeds from Stock Options Exercised	$ 0	$ 420,000	12,245,000
Preferred Stock, Liquidation Preference Per Share	$ 50	$ 0
Employee Stock Option [Member]
Stockholders Equity Note [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	147,282	58,112
Proceeds from Stock Options Exercised		$ 400,000	$ 12,200,000
Noncontrolling Interest
Stockholders Equity Note [Line Items]
Common Shares Issuable Upon Conversion Of Convertible Stock	4,220,403	4,162,996
Limited Partners' Capital Account	$ 413,300,000	$ 378,000,000
Redeemable Capital Shares Par Or Stated Value Per Share	$ 97.92	$ 90.81
Percentage of Operating Partnership net income (percent)	5.00%	5.20%	5.30%