Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Investments, Owned, Federal Income Tax Note [Line Items]
Effective income tax rate reconciliation at federal statutory income tax rate	37.00%	37.30%
Income Tax Expense (Benefit)	$ 16,168	$ 6,234
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%