Summary of Debt (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Receivables Credit Facility	Dec. 31, 2011 Receivables Credit Facility	Sep. 30, 2012 Senior Credit Facility	Dec. 31, 2011 Senior Credit Facility	Dec. 31, 2011 5.75% Senior Notes	Sep. 30, 2012 6.50% Senior Notes	Dec. 31, 2011 6.50% Senior Notes	Sep. 30, 2012 3.90% Senior Notes	Jun. 26, 2012 3.90% Senior Notes
Debt Instrument [Line Items]
Credit facility			$ 109,000	$ 109,000	$ 138,750	$ 150,000
Senior notes, net of discount							399,486	149,966	149,962	399,654	400,000
Total	797,370	808,448
Less current portion	15,000	15,000
Total long-term debt	$ 782,370	$ 793,448