Income Taxes - Deferred Income Taxes Related to Temporary Differences between Tax Bases of Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax liabilities:
Accelerated depreciation	$ 217,125	$ 221,627
Prepaid costs currently deductible	5,039	5,668
Other	5,970	5,011
Total deferred tax liabilities	228,134	232,306
Deferred tax assets:
Accrued costs not yet deductible	9,200	8,860
Allowance for doubtful accounts	536	486
Deferred revenues		2,512
Share-based compensation	2,321	2,178
Total deferred tax assets, net of valuation allowance of $0.2 million in 2020 and 2019	12,057	14,036
Deferred income taxes, net	$ 216,077	$ 218,270