Significant Accounting Policies (Narrative) (Details) - USD ($)	3 Months Ended			12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2015	Apr. 05, 2016	Jan. 06, 2016
Significant Accounting Policies [Line Items]
Capitalized development and construction salaries and other related costs	$ 600,000		$ 1,300,000
Construction, tenant improvement, and development in-progress	$ 144,900,000	$ 88,700,000		$ 88,700,000
Maximum period after cessation of major construction activity that projects are considered complete	1 year
Threshold of investment value for discontinuation of equity method accounting	$ 0
Amortization of deferred financing costs	1,169,000		953,000
Write off of unamortized deferred financing costs	0		0
Deferred leasing costs	780,000		970,000
Deferred tax asset	23,400,000
Income taxes, material adjustment amount	$ 0
General and limited partners common capital account units outstanding						100,100,852
Distributions payable, record date	Apr. 05, 2016			Jan. 06, 2016
Common unit distributions per common unit, declared	$ 0.15	$ 0.15
Distributions payable, approved date	Mar. 08, 2016	Dec. 08, 2015
Distributions payable, pay date	Apr. 15, 2016	Jan. 15, 2016
Restricted stock expense	$ 785,000		$ 313,000
Subsequent Event [Member]
Significant Accounting Policies [Line Items]
General and limited partners common capital account units outstanding					100,138,181
LTIP unit outstanding					657,373