Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Loss Carryforwards [Line Items]
Retroactive tax relief		$ 500,000
Alternative minimum tax (ATM) remaining federal tax NOL carryforwards	2,800,000
Federal net operating loss carryforward expiration year	2033
State net operating loss carryforward expiration year	2014
Current period excess stock-based compensation tax deduction	0	0	500,000
Unrecognized federal and state tax benefits	657,000	2,409,000	2,292,000	709,000
Net unrecognized tax benefits	160,000	204,000	236,000
Interest and penalties associated with unrecognized tax benefits	518,000	121,000	430,000
Interest and penalties accrued	67,000	585,000
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Gross tax credits	2,100,000
Tax carryforward period	20 years
Tax credit carryforward expiration year	2034
Alternative minimum tax (ATM) remaining federal tax NOL carryforwards	33,600,000
Deferred tax assets, operating loss carryforwad, excess tax benefits	3,100,000
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
State NOL carryforwards	5,900,000	100,000	100,000
Alternative minimum tax (ATM) remaining federal tax NOL carryforwards	58,500,000
Portion of state NOL carryforwards, not able to be utilized before expiration	8,100,000	8,300,000	6,800,000
Federal benefit	300,000	300,000	300,000
Deferred tax assets, operating loss carryforwad, excess tax benefits	1,700,000
Federal And State Tax [Member]
Operating Loss Carryforwards [Line Items]
Unrecognized federal and state tax benefits	$ 1,100,000	$ 500,000