Subsequent Events - Narrative (Details) $ / shares in Units, $ in Millions	May 15, 2019 $ / shares	Apr. 23, 2019 USD ($) ft²	Apr. 11, 2019 $ / shares	Feb. 15, 2019 $ / shares	Jan. 30, 2019 $ / shares
Series D
Subsequent Event [Line Items]
Dividend declared (in dollars per share)					$ 0.40625
Dividend paid (in dollars per share)				$ 0.40625
Series D | Subsequent event
Subsequent Event [Line Items]
Dividend declared (in dollars per share)			$ 0.40625
Series D | Scenario, Forecast
Subsequent Event [Line Items]
Dividend paid (in dollars per share)	$ 0.40625
Bellevue Corporate Plaza | Disposed of by Sale | Subsequent event
Subsequent Event [Line Items]
Gross sales price, excluding credits and closing costs | $		$ 195.0
Square footage (in sqft) | ft²		254,510