Derivatives - Narrative (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended		0 Months Ended	3 Months Ended		9 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Fair Value Hedging	Sep. 30, 2013 Fair Value Hedging	Sep. 30, 2014 Fair Value Hedging	Sep. 30, 2013 Fair Value Hedging	Mar. 31, 2012 Senior Notes Eight Point Two Five Percent Due March Fifteen Two Thousand Nineteen	Sep. 30, 2014 Senior Notes Eight Point Two Five Percent Due March Fifteen Two Thousand Nineteen	Mar. 13, 2012 Senior Notes Eight Point Two Five Percent Due March Fifteen Two Thousand Nineteen	Apr. 09, 2010 Senior Notes Four Point Nine Five Percent Due April One Two Thousand Fourteen	Mar. 31, 2014 Senior Notes Four Point Nine Five Percent Due April One Two Thousand Fourteen	Mar. 31, 2012 Senior Notes Four Point Nine Five Percent Due April One Two Thousand Fourteen	Sep. 30, 2014 Senior Notes Four Point Nine Five Percent Due April One Two Thousand Fourteen	Mar. 31, 2012 Interest Rate Swap	Sep. 30, 2014 Interest Rate Swap	Dec. 31, 2013 Interest Rate Swap	Sep. 30, 2014 Not Designated as Hedging Instrument Foreign Exchange Contract	Dec. 31, 2013 Not Designated as Hedging Instrument Foreign Exchange Contract	Sep. 30, 2014 Designated Fair Value Hedges Interest Rate Swap	Mar. 13, 2012 Designated Fair Value Hedges Interest Rate Swap	Apr. 09, 2010 Designated Fair Value Hedges Interest Rate Swap
Derivative [Line Items]
Aggregate notional value																	$ 349.1	$ 372.1	$ 190.0	$ 400.0	$ 600.0
Derivative, inception date							Mar. 13, 2012					Apr. 09, 2010
Debt instrument, face amount								238.9	450.0
Interest rate								8.25%	8.25%	4.95%		4.95%	4.95%
Maturity date							Mar. 15, 2019	Mar. 15, 2019		Apr. 01, 2014		Apr. 01, 2014	Apr. 01, 2014
Repayment of Debt	811.3	830.2						211.1			258.2	341.8
Terminated portion of interest rate swap agreement, notional amount														342.0	210.0
Payment for termination of interest rate swaps															4.2
Proceeds from termination of interest rate swaps																11.0
Reduction to interest expense			$ 0.5	$ 2.0	$ 3.3	$ 6.5