Derivative Instruments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014 interest_rate_swap_agreements
Interest rate swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Number of interest rate swap agreements	8
Notional amount of interest rate swap agreements	$ 5,750.0
Interest rate caps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of interest rate swap agreements	4,664.1
LIBOR cap rate	4.50%
Interest rate caps [Member] | Derivatives designated as hedging instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of interest rate swap agreements	$ 501.4
LIBOR cap rate	7.00%