Mortgage Notes Payable - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Interest expense capitalized	$ 13,160	$ 10,316	$ 13,052
Fair value of mortgage notes payable	$ 4,250,816	$ 4,126,819