Fair Value Measurement (Quantitative Information) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / ft²
Valuation Technique, Discounted Cash Flow [Member] | Minimum [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Holding period (years)	5 years
Average market rent rate	11.00
Average leasing costs per square foot	10.00
Valuation Technique, Discounted Cash Flow [Member] | Maximum [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Holding period (years)	10 years
Average market rent rate	16.00
Average leasing costs per square foot	35.00
Measurement Input, Discount Rate [Member] | Valuation Technique, Discounted Cash Flow [Member] | Minimum [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Financial Asset, Measurement Input	10.50%
Measurement Input, Discount Rate [Member] | Valuation Technique, Discounted Cash Flow [Member] | Maximum [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Financial Asset, Measurement Input	12.00%
Measurement Input, Cap Rate [Member] | Valuation Technique, Discounted Cash Flow [Member] | Minimum [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Financial Asset, Measurement Input	8.80%
Measurement Input, Cap Rate [Member] | Valuation Technique, Discounted Cash Flow [Member] | Maximum [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Financial Asset, Measurement Input	10.00%
Measurement Input, Price Volatility [Member] | Valuation Technique, Discounted Cash Flow [Member] | Maximum [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Financial Asset, Measurement Input	2.00%
Market Rent Growth Rate [Member] | Valuation Technique, Discounted Cash Flow [Member] | Maximum [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Financial Asset, Measurement Input	3.00%
Measurement Input, Expense Growth Rate [Member] | Valuation Technique, Discounted Cash Flow [Member] | Maximum [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Financial Asset, Measurement Input	2.00%
Measurement Input, Vacancy Rate [Member] | Valuation Technique, Discounted Cash Flow [Member] | Maximum [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Financial Asset, Measurement Input	20.00%
Measurement Input, Renewal Rate [Member] | Valuation Technique, Discounted Cash Flow [Member] | Maximum [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Non-Financial Asset, Measurement Input	70.00%
Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Property, plant, and equipment, fair value disclosure | $	$ 17,085
Fair Value, Measurements, Nonrecurring [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Property, plant, and equipment, fair value disclosure | $	$ 4,184