Investments in Unconsolidated Joint Ventures (Narrative) (Details)	12 Months Ended
	Dec. 31, 2018 property joint_venture	Dec. 31, 2017 property	Nov. 07, 2017 property	Nov. 01, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Number of real estate properties	214	205
Seattle, Hong Kong, Tokyo, Osaka
Schedule of Equity Method Investments [Line Items]
Ownership percentage in the Operating Partnership	50.00%
Number of joint ventures | joint_venture	4
PREI ®
Schedule of Equity Method Investments [Line Items]
Ownership percentage in the Operating Partnership	20.00%	20.00%			20.00%
Number of joint ventures	1
Number of real estate properties	10
Prudential Real Estate Investors and Griffin Capital Essential Asset REIT, Inc.
Schedule of Equity Method Investments [Line Items]
Number of joint ventures | joint_venture	2
GCEAR
Schedule of Equity Method Investments [Line Items]
Ownership percentage in the Operating Partnership	20.00%	20.00%			20.00%
Number of real estate properties	1
1101 Space Park Drive
Schedule of Equity Method Investments [Line Items]
Ownership percentage in the Operating Partnership	17.00%	17.00%			17.00%
Mitsubishi
Schedule of Equity Method Investments [Line Items]
Ownership percentage in the Operating Partnership	50.00%	50.00%		50.00%
Number of real estate properties			2