Reconciliation of Asset Retirement Obligations which are Included in Other Liabilities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of period	$ 4,314	$ 3,286
Changes in estimates	(2)	354
Liabilities incurred	290	335
Liabilities settled	(67)	(8)
Acquisitions of properties	(83)	(385)
Asset Retirement Obligation, Sale of Properties	0	(310)
Accretion expense	316	272
Balance at end of period	$ 4,934	$ 4,314