Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Investments, Owned, Federal Income Tax Note [Line Items]
Effective income tax rate reconciliation at federal statutory income tax rate			36.90%	42.40%
Income Tax Expense (Benefit)	$ 16,672	$ 10,835	$ 22,907	$ 17,319
U.S. Federal
Investments, Owned, Federal Income Tax Note [Line Items]
Effective income tax rate reconciliation at federal statutory income tax rate			35.00%	35.00%