Held for Sale/Disposed Assets - Narrative (Details) $ in Millions		6 Months Ended
	Jul. 23, 2020 USD ($)	Jun. 30, 2020 USD ($) property	Jun. 30, 2019 USD ($) property
Los Angeles | Disposed of by sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property			1
Los Angeles | Disposed of by sale | Disposed Assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales price			$ 12.4
Gain on sale of real estate			$ 4.5
Washington D.C. | Disposed of by sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property		3
Washington D.C. | Disposed of by sale | Disposed Assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales price		$ 51.3
Gain on sale of real estate		17.8
Third-party purchaser | Seattle | Held-for-Sale | Disposed Assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net book value		$ 11.8
Industrial building | Third-party purchaser | Subsequent event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales price	$ 22.2