Non-controlling Interests (Details) - USD ($) $ in Thousands		6 Months Ended	12 Months Ended
	Jan. 02, 2013	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Noncontrolling Interest [Line Items]
Stockholders' Equity Attributable to Noncontrolling Interest		$ 13,708	$ 20,862
Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Stockholders' Equity Attributable to Noncontrolling Interest		$ 13,708	$ 20,862	$ 11,030	$ 7,116
Non-controlling interest in Operating Partnership [Member] | Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Operating Partnership Units Issued	212,000
Operating Partnership Units		212,000	212,000
Noncontrolling Interest in Operating Partnerships		$ 4,100	$ 4,000
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		0.70%	0.70%
Non-controlling interest of joint venture partner [Member] | Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Stockholders' Equity Attributable to Noncontrolling Interest		$ 9,400	$ 16,700