Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Taxes [Line Items]
Effective tax rate	27.90%	21.30%	(39.30%)	21.00%
Income tax expense	$ 24,408,000	$ 28,755,000	$ 12,505,000	$ 33,995,000
Statute of limitations expiration date			Jun. 30, 2014
Reasonably possible decrease in liability related to uncertain tax positions within twelve months of the current reporting date	$ 29,400,000		$ 29,400,000