Deferred Costs (Textual) (Details) $ in Thousands	1 Months Ended	8 Months Ended	12 Months Ended			20 Months Ended
	May 31, 2015 ft²	Dec. 31, 2015 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($)
Deferred Costs (Textual) [Abstract]
Capitalized internal direct leasing costs			$ 4,600	$ 5,000	$ 6,600
2015 Lease [Member]
Deferred Costs (Textual) [Abstract]
Square feet of office space leased | ft²	228,000
Brokerage commission						$ 4,200
2015 Lease [Member] | Chairman and Lead Independent Director [Member]
Deferred Costs (Textual) [Abstract]
Membership interest	33.30%
Brokerage commission		$ 500		$ 500		$ 1,000
2015 Lease [Member] | WDL Real Estate Advisory Group, LLC [Member]
Deferred Costs (Textual) [Abstract]
Membership interest	49.00%