Fair Value Measurements (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Interest Rate Caps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate caps	$ 3		$ 159
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	2,072,177	[1]	2,255,951	[1]
Fair Value, Measurements, Recurring [Member] | Interest Rate Caps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate caps	3	[2]	159	[2]
Fair Value, Measurements, Recurring [Member] | Quoted Market Prices in Active Markets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	2,072,177	[1]	2,255,951	[1]
Fair Value, Measurements, Recurring [Member] | Quoted Market Prices in Active Markets (Level 1) [Member] | Interest Rate Caps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate caps	0	[2]	0	[2]
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	[1]	0	[1]
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Interest Rate Caps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate caps	3	[2]	159	[2]
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	[1]	0	[1]
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Interest Rate Caps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate caps	$ 0	[2]	$ 0	[2]

[1] The Company has short-term investments classified as cash equivalents as the original maturities are less than 90 days.

[2] As of December 31, 2014 and 2013, the Company has 4 and 22 interest rate cap agreements, respectively, with an aggregate fair value of approximately $3,000 and $0.2 million, respectively, based on quoted market values from the institutions holding the agreements.