Real Estate - Summary of Dispositions (Detail) ft² in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($) ft² Property	Sep. 30, 2016 USD ($) ft² Property	Sep. 30, 2017 USD ($) ft² Property	Sep. 30, 2016 USD ($) ft² Property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gains on dispositions of investments in real estate and revaluation of equity investments upon acquisition of a controlling interest, net	$ 779,053	$ 117,296	$ 959,384	$ 461,963
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	697,906	117,296	878,237	375,348
Gains on dispositions of investments in real estate and revaluation of equity investments upon acquisition of a controlling interest, net	$ 779,053	$ 117,296	$ 959,384	$ 461,963
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	201	11	211	21
Square feet | ft²	41,776	2,657	45,420	6,676
Net proceeds	$ 2,356,322	$ 185,811	$ 2,869,428	$ 649,511
Gains on contributions, net (2)	$ 647,647	$ 29,197	$ 773,715	$ 132,787
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	7	48	45	147
Square feet | ft²	2,179	5,041	8,217	15,606
Net proceeds	$ 155,227	$ 410,602	$ 614,906	$ 1,300,209
Gains on contributions, net (2)	50,259	88,099	104,522	242,561
Continuing Operations [Member] | Revaluation of equity investments upon acquisition of controlling interest and redemption of investment in co-investment ventures [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gains on contributions, net (2)	$ 81,147	$ 0	$ 81,147	$ 86,615