Investments in Unconsolidated Joint Ventures (Statements of Operations of the Joint Ventures) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule of Equity Method Investments [Line Items]
Total revenue		$ 654,773	$ 733,741	$ 1,407,329	$ 1,459,508
Expenses
Transaction costs		332	417	947	877
Depreciation and amortization		178,188	177,411	349,282	342,005
Total expenses		460,507	482,353	941,694	957,944
Other income (expense)
Interest expense		(107,142)	(102,357)	(208,733)	(203,366)
Gain on sales of real estate		203,767	1,686	613,932	781
Net income		298,580	203,461	875,726	334,620
Income from unconsolidated joint ventures		1,832	47,964	1,463	48,177
Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Total revenue	[1]	89,563	80,204	182,766	163,159
Expenses
Operating		33,704	30,134	69,105	60,633
Depreciation and amortization		37,390	24,818	69,425	53,464
Total expenses		71,094	54,952	138,530	114,097
Other income (expense)
Interest expense		(23,306)	(20,803)	(45,889)	(41,560)
Gain on sales of real estate		11,720	34,572	11,720	34,572
Net income		6,883	39,021	10,067	42,074
Company's share of net income		4,024	22,376	5,276	23,960
Basis differential	[2]	(2,192)	25,588	(3,813)	24,217
Income from unconsolidated joint ventures		1,832	47,964	1,463	48,177
Straight-line rent adjustments		8,500	7,600	18,200	13,400
Colorado Center [Member]
Other income (expense)
Straight-line rent adjustments		400	500	900	1,100
Above and below market rent adjustments, net		$ 200	$ 400	$ 500	$ 800

[1] Includes straight-line rent adjustments of approximately $8.5 million and $7.6 million for the three months ended June 30, 2020 and 2019, respectively, and $18.2 million and $13.4 million for the six months ended June 30, 2020 and 2019, respectively.

[2] Includes straight-line rent adjustments of approximately $0.4 million and $0.5 million for the three months ended June 30, 2020 and 2019, respectively, and $0.9 million and $1.1 million for the six months ended June 30, 2020 and 2019, respectively. Also includes net above-/below-market rent adjustments of approximately $0.2 million and $0.4 million for the three months ended June 30, 2020 and 2019, respectively, and $0.5 million and $0.8 million for the six months ended June 30, 2020 and 2019, respectively.