Real Estate - Summary of Property Acquired (Details) $ in Thousands	3 Months Ended
Mar. 31, 2020 USD ($) ft²
Real Estate [Line Items]
Purchase Price	$ 4,200,000
Pepsi Bottling Ventures
Real Estate [Line Items]
Purchase Price	$ 34,937
Approximate Square Feet \| ft²	526,320
Acquisition Fees and Expenses	$ 386

Acquisition-related costs incurred to effect a business combination, which are paid to affiliates and expensed during the period. Such costs include a fee of 2.5% of the contract purchase price of each property acquired by the company, and reimbursement for actual acquisition expenses incurred during the period.

No definition available.

Name:	gcnl_AssetAcquisitionAcquisitionFeesAndExpensestoAffiliates
Namespace Prefix:	gcnl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration