Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred Income Tax Assets And Liabilities [Line Items]
Asset reserves and liabilities not yet deductible for tax	$ 21,482	$ 28,247
Tax over book basis of certain assets	1,001	1,451
Net operating loss and tax credit carryforwards	3,782	5,130
Intangible contract value	699	262
Other	68	103
Total noncurrent deferred tax assets	27,032	35,193
Less valuation allowance	(848)	(3,865)
Total noncurrent deferred tax assets	26,184	31,328
Book over tax basis of certain assets	(11,305)	(11,478)
Intangible value	(2,149)	(2,264)
Other	(1,617)	(1,528)
Total noncurrent deferred tax liabilities	(15,071)	(15,270)
Net total noncurrent deferred tax assets	$ 11,113	$ 16,058