Cash and Cash Equivalents - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 373,084	$ 175,523	$ 158,249	$ 185,245
Notional Pooling Arrangement [Member]
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	11,060	3,569
Outstanding A/P checks [member]
Cash and Cash Equivalents [Line Items]
Outstanding A/P Checks	11,790	12,989
Outstanding payroll checks [Member]
Cash and Cash Equivalents [Line Items]
Outstanding A/P Checks	$ 446	$ 848