Organization - Narrative (Details) $ / shares in Units, $ in Thousands					3 Months Ended	12 Months Ended		24 Months Ended	27 Months Ended
		Apr. 30, 2019 $ / shares shares	Dec. 14, 2018 shares	Sep. 20, 2017 USD ($)	Sep. 30, 2018	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 18, 2019 $ / shares	May 01, 2019 shares	Jun. 30, 2015 shares
Subsidiary, Sale of Stock [Line Items]
Exchange ratio		1.04807
Common Stock, par value (in usd per share) | $ / shares						$ 0.001	$ 0.001		$ 0.001	$ 0.001
Exchange ratio		1.04807
Common stock, number of shares outstanding (in shares)		78,054,934				227,853,720	174,278,341		227,853,720		252,863,421
GCEAR's operating partnership units outstanding		527,045
Repurchase of noncontrolling interest (shares)						6,000	0
Ownership interest (percent)						87.70%
Proceeds from issuance of equity | $								$ 2,700,000	$ 2,700,000
Common stock issued | $	[1]					$ 228	$ 174		$ 228
Sponsor and Affiliates
Subsidiary, Sale of Stock [Line Items]
Limited liability partnership interest held (percent)						10.60%			10.60%
Third parties
Subsidiary, Sale of Stock [Line Items]
Limited liability partnership interest held (percent)						1.70%			1.70%
Follow-on Offering
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance of private placement | $				$ 2,200,000					$ 80,700
Implied EA-1 common stock issued in consideration						8,412,006			8,412,006
Distribution Reinvestment Plan
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance of private placement | $				200,000
Common stock issued | $						$ 293,700	252,800		$ 293,700
Private Offering
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance of private placement | $				$ 2,000,000
Implied EA-1 common stock issued in consideration						281,468,829.57			281,468,829.57
Signature Office REIT Merger
Subsidiary, Sale of Stock [Line Items]
Implied EA-1 common stock issued in consideration												43,772,611
Common Class E
Subsidiary, Sale of Stock [Line Items]
Exchange ratio		1.04807
Common Stock, par value (in usd per share) | $ / shares		$ 0.001
Exchange ratio		1.04807
Number of shares issued (in shares)		174,981,547
Units issued upon conversion (in shares)		1
Common stock, number of shares outstanding (in shares)						154,151,658			154,151,658
Cumulative Perpetual Convertible Preferred Stock
Subsidiary, Sale of Stock [Line Items]
Shares issued upon conversion (shares)		1
Series A Preferred Stock
Subsidiary, Sale of Stock [Line Items]
Number of shares issued (in shares)		5,000,000
Common stock, number of shares outstanding (in shares)											5,000,000
Common Stock
Subsidiary, Sale of Stock [Line Items]
Perpetual convertible preferred shares and Common stock subject to redemption | $						$ 20,565	$ 11,523		$ 20,565
Share Redemption Program
Subsidiary, Sale of Stock [Line Items]
Share limit under the repurchase program (percent), Redemption, Percentage of Weighted Average Shares Outstanding					5.00%
Board of Directors Chairman
Subsidiary, Sale of Stock [Line Items]
Partnership units owned (shares)						2,400,000			2,400,000
GRECO
Subsidiary, Sale of Stock [Line Items]
Number of units exchanged (shares)			20,438,684
Operating Partnership Units
Subsidiary, Sale of Stock [Line Items]
GCEAR's operating partnership units outstanding											284,533,435

[1] See Note 10, Equity, for the number of shares outstanding of each class of common stock as of December 31, 2019.