Derivative Instruments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013 interest_rate_swap_agreements
Interest Rate Swap [Member]
Derivative [Line Items]
Number of interest rate swap agreements	8
Notional amount of derivative	$ 5,750.0
Interest Rate Cap [Member]
Derivative [Line Items]
Notional amount of derivative	4,664.1
LIBOR cap rate	4.50%
Interest Rate Cap [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of derivative	$ 501.4
LIBOR cap rate	7.00%