Equity Incentive Compensation Plans and Other Employee Benefits - Deferred Compensation Liability (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Deferred Compensation Liability [Roll Forward]
Beginning deferred compensation liability balance	$ 1,749	$ 1,447
Employee contributions	370	244
Company matching contributions	198	116
Distributions	(806)	(274)
Participant earnings (losses)	(119)	216
Ending deferred compensation liability balance	1,392	1,749
Deferred Compensation Liability [Abstract]
Amount to be paid within one year	94	169
Remaining balance to be paid beyond one year	$ 1,298	$ 1,580