Income Tax Asset (Liability) (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Net income tax asset (liability)	$ 1	$ 576
State and Local Jurisdiction
Income Taxes [Line Items]
Current state income tax asset (liability)	$ 1	1
Deferred state income tax asset (liability)		$ 575