Real Estate - Investments in Real Estate Properties (Detail) ft² in Thousands, $ in Thousands	Mar. 31, 2017 USD ($) ft² a Buildings	Dec. 31, 2016 USD ($) ft² a Buildings
Real Estate Properties [Line Items]
Total investments in real estate properties	$ 27,131,229	$ 27,119,330
Less accumulated depreciation	3,914,817	3,758,372
Net investments in real estate properties	$ 23,216,412	$ 23,360,958
Improved Land [Member]
Real Estate Properties [Line Items]
Square Feet | ft²	0	0
Number of buildings | Buildings	0	0
Total investments in real estate properties	$ 6,038,816	$ 6,037,543
Building and Improvements [Member]
Real Estate Properties [Line Items]
Square Feet | ft²	329,743	331,210
Number of buildings | Buildings	1,762	1,776
Total investments in real estate properties	$ 17,911,386	$ 17,905,914
Development Portfolio, Including Cost of Land: Pre-stabilized [Member]
Real Estate Properties [Line Items]
Square Feet | ft²	7,784	8,256
Number of buildings | Buildings	26	29
Total investments in real estate properties	$ 725,949	$ 798,233
Properties Under Development [Member]
Real Estate Properties [Line Items]
Square Feet | ft²	19,133	19,539
Number of buildings | Buildings	54	60
Total investments in real estate properties	$ 761,509	$ 633,849
Land [Member]
Real Estate Properties [Line Items]
Square Feet | a	5,665	5,892
Total investments in real estate properties	$ 1,162,427	$ 1,218,904
Other Real Estate Investments [Member]
Real Estate Properties [Line Items]
Square Feet | ft²	0	0
Number of buildings | Buildings	0	0
Total investments in real estate properties	$ 531,142	$ 524,887