Income Taxes - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Estimated federal taxable income	$ 362,387	$ 187,064
Statutory federal income tax rate	35.00%
Effective tax rate	36.36%	34.35%	37.65%
Income tax expense reduction		9,154
Unrecognized tax benefits that would affect effective tax rate	28,467
Reversal of accrued interest on unrecognized tax benefits		4,116
Accrued interest on unrecognized tax benefits	625		2,076
Total accrued interest on unrecognized tax benefits	21,281	20,658
Reduction in unrecognized tax benefits	$ 6,527