Long Term Debt - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Debt Instrument [Line Items]
Long-term debt, percentage bearing variable interest rate	0.96%
Interest rate on notional value	1.415%
Minimum interest expense coverage ratio	3.0
Maximum debt to cash flow ratio	3.25
Forward Starting Interest Rate Swap Agreement
Debt Instrument [Line Items]
Interest rate swap agreements, notional amount	150.0
2011 Refinancing Credit Agreement
Debt Instrument [Line Items]
Debt instrument, effective issuance date	Nov. 07, 2011
Deferred financing cost	1.9
Maturity date of debt instrument	2016-11-07
Debt instrument, interest rate, effective percentage	0.50%
Debt instrument basis points spread on variable rate	100
Revolving Credit Facility | 2011 Refinancing Credit Agreement
Debt Instrument [Line Items]
Revolving credit facility, amount	600
Credit facility loan term, years	5
Letter of Credit
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity	61.9
Line of credit facility, amount currently available	271.1
Base Rate | 2011 Refinancing Credit Agreement
Debt Instrument [Line Items]
Debt instrument basis points spread on variable rate	0
Base Rate | 2011 Refinancing Credit Agreement | Minimum
Debt Instrument [Line Items]
Debt instrument basis points spread on variable rate	0
Base Rate | 2011 Refinancing Credit Agreement | Maximum
Debt Instrument [Line Items]
Debt instrument basis points spread on variable rate	75
Alternative Rate | 2011 Refinancing Credit Agreement
Debt Instrument [Line Items]
Debt instrument basis points spread on variable rate	75
Alternative Rate | 2011 Refinancing Credit Agreement | Minimum
Debt Instrument [Line Items]
Debt instrument basis points spread on variable rate	75
Alternative Rate | 2011 Refinancing Credit Agreement | Maximum
Debt Instrument [Line Items]
Debt instrument basis points spread on variable rate	175
Interest Rate Swap Contracts
Debt Instrument [Line Items]
Debt instrument, effective issuance date	Jul. 31, 2013
Debt instrument, termination date	2016-11-07
6.875% Senior Notes, Due 2013
Debt Instrument [Line Items]
Maturity date of debt instrument	2013
Senior Notes issued	150.0
Debt Instrument, Interest Rate, Stated Percentage	6.875%