Segment Information - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	3
Number of operating segments | segment	3
Other assets, net | $	$ 263,923	$ 112,955
Third-Party Real Estate Services Segment
Segment Reporting Information [Line Items]
Other assets, net | $	$ 45,700