Basis of Presentation and Significant Accounting Policies - Narrative (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2018 USD ($) segment	Mar. 31, 2017 USD ($)	Dec. 31, 2017
Significant Accounting Policies [Line Items]
Land Sales | $	$ 0	$ 0
Number of reportable segments | segment	7
Minimum
Significant Accounting Policies [Line Items]
Percentage of sales price fee from construction management agreements			300.00%
Maximum
Significant Accounting Policies [Line Items]
Percentage of sales price fee from construction management agreements			5.00%