Organization and Basis of Presentation Rental Revenue from USG (Tables)

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block]

Only the U.S. federal government accounted for 10% or more of our rental revenue, which consists of property rentals and tenant reimbursements, as follows:

	Year Ended December 31,
(Dollars in thousands)	2018			2017			2016
Rental revenue from the U.S. federal government	$	94,822		$	92,192		$	103,864
Percentage of commercial segment rental revenue	22.0		%	24.0		%	29.1		%
Percentage of total rental revenue	17.6		%	19.4		%	23.6		%