Debt - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
	Mar. 31, 2013 Y	Jun. 30, 2012 Y
Debt Instrument
Revolving credit agreement period (in years)	5
Credit facility maximum borrowing capacity	$ 300
Credit facility agreement expiration date	Jun. 15, 2017
Credit facility, number of one-year extensions	2
Credit facility, duration of extension term (in years)	1
Credit facility outstanding balance	0
Credit facility borrowing capacity	300
Term loan, face amount		300
Term of loan, years		5
Repayment terms		Term loan is payable in quarterly installments, which commenced on June 30, 2012, with all remaining principal due in April 2016.
Interest rate on term loan	1.25%
Term loan payable	$ 285