Derivative Instruments - Fair Values of Derivative Instruments (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Derivative Asset	$ 0		$ 0
Derivative Liability, Fair Value	(130.8)		(165.9)
Accrued Liabilities [Member] | Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	0		0
Derivative Liability, Fair Value			0
Deferred credits and other [Member] | Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	0		0
Derivative Liability, Fair Value	0
Deferred charges and other [Member] | Interest rate caps [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	0		0
Derivatives not designated as hedging instruments [Member] | Deferred charges and other [Member] | Interest rate caps [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	0	[1]	0	[1]
Fair Value, Measurements, Recurring [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	130.8		165.9
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	$ 130.8		$ 165.9

[1] Amount rounds to zero.