Reconciliation of Statutory Federal Income Tax (Benefit) Expense Reported in Net Income to Combined Actual Income Tax (Benefit) Expense (Parenthetical) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Provision of Income Taxes [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%
Income tax (benefit) expense, adjustment to deferred taxes	$ (1,400,000)	$ 600,000.0