Redeemable Preferred Stock (Details)			3 Months Ended		9 Months Ended
	Feb. 14, 2020 USD ($) $ / shares shares	Sep. 27, 2019 $ / shares	Sep. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($) $ / shares	Sep. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($) $ / shares	Dec. 31, 2019 USD ($) $ / shares shares
Class of Stock [Line Items]
gross potential offering proceeds			$ 3,000,000,000		$ 3,000,000,000
Common Stock, Dividends, Per Share, Declared | $ / shares			$ 0.175	$ 0.2625	$ 0.6125	$ 0.785
Proceeds from Other Equity					$ 1,356,921,000
daycountvolweightedavgcalcformarketvalue			20		20
aggregate offering costs			$ 147,811,000		$ 147,811,000
prorataamountofferingcostsreclassed					16,322,000
deferred offering costs not yet reclassified			4,721,000		4,721,000
shares common stock from warrant exercises | shares	20
Deferred offering costs			21,043,000		21,043,000
specifically identifiable offering costs					126,768,000
Aggregate Offering Expenses, Maximum As a Percentage Of Gross Proceeds		12.00%
Sale of Stock, Price Per Share | $ / shares		$ 1,000
Preferred Stock, Par or Stated Value Per Share | $ / shares	$ 0.01
Dividends, Common Stock, Cash			$ 8,876,000	$ 11,823,000	$ 29,991,000	$ 34,599,000
Sale Of Stock, Maximum Consideration Received On Transaction	$ 1,500,000,000
Series A Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage					6.00%
preferred stock | shares			2,226,000		2,226,000		2,161,000
Preferred Stock, Par or Stated Value Per Share | $ / shares			$ 0.01		$ 0.01		$ 0.01
Preferred Stock, Value, Issued			$ 20,000		$ 20,000		$ 20,000
Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Sale Of Stock, Maximum Shares Sold | shares	1,000,000
Equity Or Debt Securities [Member]
Class of Stock [Line Items]
Sale Of Stock, Maximum Consideration Received On Transaction	$ 100,000,000
Equity Securities [Member]
Class of Stock [Line Items]
Sale Of Stock, Maximum Consideration Received On Transaction	400,000,000
Common Stock [Member]
Class of Stock [Line Items]
Common Stock, Shares, Issued | shares			49,901,000		49,901,000		46,443,000
Sale Of Stock, Maximum Consideration Received On Transaction	$ 125,000,000
$1.5 billion unit [Domain]
Class of Stock [Line Items]
maximum shares available to be issued | shares			1,500,000		1,500,000
Unit Offering [Member]
Class of Stock [Line Items]
gross potential offering proceeds			$ 1,500,000,000		$ 1,500,000,000
Proceeds from Other Equity					1,236,414,000
aggregate offering costs			131,524,000		131,524,000
prorataamountofferingcostsreclassed					15,874,000
deferred offering costs not yet reclassified			0		0
Deferred offering costs			15,874,000		15,874,000
specifically identifiable offering costs					115,650,000
2016 Shelf Offering [Member] [Domain]
Class of Stock [Line Items]
gross potential offering proceeds			400,000,000		400,000,000
Proceeds from Other Equity					4,614,000
aggregate offering costs			1,089,000		1,089,000
prorataamountofferingcostsreclassed					22,000
deferred offering costs not yet reclassified			975,000		975,000
Deferred offering costs			997,000		997,000
specifically identifiable offering costs					92,000
series A1M1 offering [Domain]
Class of Stock [Line Items]
gross potential offering proceeds			1,000,000,000		1,000,000,000
Proceeds from Other Equity					115,893,000
aggregate offering costs			14,700,000		14,700,000
prorataamountofferingcostsreclassed					426,000
deferred offering costs not yet reclassified			3,251,000		3,251,000
Deferred offering costs			3,677,000		3,677,000
specifically identifiable offering costs					11,023,000
preferred office growth fund [Domain]
Class of Stock [Line Items]
gross potential offering proceeds			100,000,000		100,000,000
Proceeds from Other Equity					0
aggregate offering costs			498,000		498,000
prorataamountofferingcostsreclassed					0
deferred offering costs not yet reclassified			495,000		495,000
Deferred offering costs			$ 495,000		495,000
specifically identifiable offering costs					$ 3,000