Real Estate - Summary of Dispositions (Detail) ft² in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) ft² Property	Sep. 30, 2017 USD ($) ft² Property	Sep. 30, 2018 USD ($) ft² Property	Sep. 30, 2017 USD ($) ft² Property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square feet | ft²	523	6,328	1,406	6,478
Total gains on dispositions of investments in real estate and revaluation of equity investments upon acquisition of a controlling interest, net	$ 194,058	$ 779,053	$ 483,430	$ 959,384
Continuing Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total gains on contributions and dispositions, net	194,058	697,906	483,430	878,237
Total gains on dispositions of investments in real estate and revaluation of equity investments upon acquisition of a controlling interest, net	$ 194,058	$ 779,053	$ 483,430	$ 959,384
Continuing Operations [Member] | Contributions to unconsolidated co-investment ventures [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | Property	13	201	24	211
Square feet | ft²	4,192	41,776	8,434	45,420
Net proceeds	$ 385,001	$ 2,356,322	$ 1,050,740	$ 2,869,428
Gains on contributions, dispositions or revaluation, net	$ 129,222	$ 647,647	$ 330,475	$ 773,715
Continuing Operations [Member] | Dispositions to Third Parties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | Property	6	7	24	45
Square feet | ft²	1,827	2,179	7,269	8,217
Net proceeds	$ 147,408	$ 155,227	$ 549,530	$ 614,906
Gains on contributions, dispositions or revaluation, net	64,836	50,259	152,955	104,522
Continuing Operations [Member] | Revaluation of equity investments upon acquisition of controlling interest [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gains on contributions, dispositions or revaluation, net	$ 0	$ 81,147	$ 0	$ 81,147