Segment Information - Narrative (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($) segment	Jun. 30, 2017 segment	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	3
Number of operating segments | segment		3
Other assets, net | $	$ 273,722		$ 263,923
Third-Party Real Estate Services Segment
Segment Reporting Information [Line Items]
Other assets, net | $	$ 42,100		$ 45,700