Real Estate - Investments in Real Estate Properties (Detail) ft² in Thousands, $ in Thousands	Dec. 31, 2015 USD ($) ft² Buildings	Dec. 31, 2014 USD ($) ft² Buildings
Real Estate Properties [Line Items]
Total investments in real estate properties	$ 27,521,368	$ 22,190,145
Less accumulated depreciation	3,274,284	2,790,781
Net investments in real estate properties	24,247,084	19,399,364
Improved Land [Member]
Real Estate Properties [Line Items]
Total investments in real estate properties	$ 5,874,052	$ 4,227,637
Building and Improvements [Member]
Real Estate Properties [Line Items]
Square Feet and Acres | ft²	333,830	282,282
Number of buildings | Buildings	1,872	1,607
Total investments in real estate properties	$ 17,861,693	$ 14,407,815
Development Portfolio, Including Cost of Land: Pre-stabilized [Member]
Real Estate Properties [Line Items]
Square Feet and Acres | ft²	12,598	7,448
Number of buildings | Buildings	28	24
Total investments in real estate properties	$ 918,099	$ 547,982
Properties Under Development [Member]
Real Estate Properties [Line Items]
Square Feet and Acres | ft²	19,630	22,844
Number of buildings | Buildings	63	55
Total investments in real estate properties	$ 954,804	$ 925,998
Land [Member]
Real Estate Properties [Line Items]
Square Feet and Acres | ft²	7,404	9,017
Total investments in real estate properties	$ 1,359,794	$ 1,577,786
Other Real Estate Investments [Member]
Real Estate Properties [Line Items]
Total investments in real estate properties	$ 552,926	$ 502,927