Equity Transactions (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Apr. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Excess of redemption value of preferred stock over the carrying value		$ 0	$ 2,541	$ 0
Sale of common stock, net (in shares)		345,444	0
Share issued, price per share (in dollars per share)		$ 260.38
Proceeds from issuance from common stock		$ 89,055	$ (384)	$ 332,137
General partner ownership interest		96.70%	96.70%
Redemption value of operating partnership units outstanding		$ 547,500	$ 520,200
Series H 7.125% Cumulative Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Shares outstanding (in shares)	2,950,000
Cumulative dividend rate (in hundredths)	7.125%
Liquidation preference (in dollars per share)	$ 25.00
Liquidation preference	$ 73,800
Excess of redemption value of preferred stock over the carrying value	$ 2,500
Operating Partnership Units [Member]
Class of Stock [Line Items]
Shares outstanding (in shares)		2,054,814	2,056,263
Long Term Incentive Plan 2014 Units [Member]
Class of Stock [Line Items]
Shares outstanding (in shares)		213,299	181,027
Long Term Incentive Plan Z Units and LTIP Units [Member]
Class of Stock [Line Items]
Converted (in shares)		0	0	0