Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred Income Tax Assets And Liabilities [Line Items]
Asset reserves and liabilities not yet deductible for tax	$ 28,247	$ 21,742
Tax over book basis of certain assets	1,451	1,665
Net operating loss and tax credit carryforwards	5,130	5,483
Intangible contract value	262	148
Other	103	123
Total noncurrent deferred tax assets	35,193	29,161
Less valuation allowance	(3,865)	(3,986)
Total noncurrent deferred tax assets	31,328	25,175
Book over tax basis of certain assets	(11,478)	(5,707)
Intangible value	(2,264)	(2,370)
Other	(1,528)	(2,151)
Total noncurrent deferred tax liabilities	(15,270)	(10,228)
Net total noncurrent deferred tax assets	$ 16,058	$ 14,947