Stock Based Compensation (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation expense	$ 998	$ 730	$ 1,953	$ 1,368
Expected vesting percent					50.00%
2015 LTIP (performance-based)
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation expense	508	622	998	1,153
2017 LTIP (time-based)
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation expense	371	0	714	0
ESPP
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation expense	15	0	30	0
Board Of Directors | Board of Directors restricted stock | Restricted Stock
Share based Compensation Allocation of Recognized Period Cost [Line Items]
Total stock based compensation expense	$ 104	$ 108	$ 211	$ 215