Income Taxes - Reconciliation of Income Tax at U.S. Statutory Rate to Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State tax expense, net of federal benefit	2.30%	6.30%	3.70%
Tax credits	2.10%	(0.00%)	(0.00%)
Other nondeductible expenses	(0.20%)	9.20%	3.40%
Effect of change in income tax rates	0.10%	(2.20%)	(1.90%)
Impact of state net operating losses	0.00%	23.20%	5.40%
Stock options	(0.20%)	0.00%	0.10%
Other	1.50%	(1.90%)	0.00%
Expired net operating losses	(1.40%)	0.00%	15.70%
Change in valuation allowance	0.50%	(12.20%)	(283.00%)
Total expense	39.70%	57.40%	(221.60%)