Fair Value Measurements (Narrative) (Details) ft² in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($) ft²	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) ft² property	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of impaired properties | property			1
Area of real estate property | ft²	7		7
Real estate investment, net	$ 2,800		$ 2,800
Impairment of real estate assets	1,430	$ 0	1,430	$ 0
Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real estate investment, net	1,400		1,400
Significant Other Observable Inputs (Level 2) | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument fair value disclosure	2,260,000		2,260,000		$ 2,080,000
Significant Other Observable Inputs (Level 2) | Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument fair value disclosure	$ 2,240,000		$ 2,240,000		$ 2,080,000