Equity Transactions (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Apr. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2018
Class of Stock [Line Items]
Excess of redemption value of preferred stock over the carrying value		$ 0	$ 0	$ 2,541
Common stock, shares authorized		670,000,000	670,000,000
Proceeds from issuance from common stock		$ (919)	$ 89,055	$ (384)
General partner ownership interest		96.60%	96.70%
Redemption value of operating partnership units outstanding		$ 565,300	$ 547,500
ATM Program, 2018 [Member]
Class of Stock [Line Items]
Common stock, shares authorized		900,000,000.0			900,000,000.0
ATM Program, 2016 [Member]
Class of Stock [Line Items]
Sale of common stock, net (in shares)			345,444
Share issued, price per share (in dollars per share)			$ 260.38
Proceeds from issuance from common stock			$ 89,100
Series H 7.125% Cumulative Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Number of shares outstanding	2,950,000
Cumulative dividend rate	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]
Number of shares outstanding		2,171,309	2,054,814
Long Term Incentive Plan 2014 Units [Member]
Class of Stock [Line Items]
Number of shares outstanding		134,080	213,300