Equity Transactions (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Apr. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Excess of redemption value of preferred stock over the carrying value		$ 2,541	$ 0	$ 0
Proceeds from issuance from common stock		$ (384)	$ 332,137	$ 531,379
General partner ownership interest (in hundredths)		96.70%	96.70%
Redemption value of operating partnership units outstanding		$ 520,200	$ 530,200
Series H 7.125% Cumulative Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Shares issued (in shares)			2,950,000
Shares outstanding (in shares)	2,950,000
Cumulative dividend rate (in hundredths)		0.00%	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
Common Stock [Member]
Class of Stock [Line Items]
Common stock, number of shares sold		0	1,481,737
Common stock issued, average share price (in dollars per share)			$ 226.46
Proceeds from issuance from common stock			$ 332,300
Operating Partnership Units [Member]
Class of Stock [Line Items]
Shares outstanding (in shares)		2,056,263	2,070,360
Long Term Incentive Plan 2014 Units [Member]
Class of Stock [Line Items]
Shares outstanding (in shares)		181,027	144,185