Income Taxes - Components of Deferred Taxes (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Net operating losses	$ 109,236	$ 107,655
Book/tax differences in deferred income	4,657	5,302
Book/tax differences in acquired assets	(39,054)	(36,732)
Total deferred tax asset	74,839	76,225
Valuation allowance	(74,839)	(76,225)
Total deferred tax asset, net	$ 0	$ 0