Income Tax - Segregation of Income Tax Provision Based on Location of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current
Federal	$ 0	$ 0	$ 0
State			6
Total current			6
Deferred
State			540
Total deferred			540
Total income tax expense (benefit)			$ 546