Fair Value Disclosure of Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Fixed Rate Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes Payable, fair value	$ 3,120.0	$ 3,130.0
Notes Payable Excluding Interest Rate Swaps and Cap Agreements	2,980.0	3,000.0
Variable Rate Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes Payable, fair value	1,591.4	1,511.3
Notes Payable Excluding Interest Rate Swaps and Cap Agreements	$ 1,580.0	$ 1,500.0
Maximum [Member] | Conventional Variable Rate Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Renewal Period	90 days
Minimum [Member] | Conventional Variable Rate Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Renewal Period	30 days