Income Taxes - Summary of Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Statutory income tax rate	21.00%	21.00%	35.00%
Effect of statutory depletion	(3.40%)	(3.40%)	(5.60%)
State income taxes, net of federal tax benefit	2.00%	2.80%	1.50%
Change in tax status of subsidiary	(1.70%)
Stock based compensation	(0.50%)	(0.50%)	(1.00%)
Impact from 2017 Tax Act		(3.30%)	(41.70%)
Domestic production deduction			(2.20%)
Other items	0.80%	1.70%	(1.30%)
Effective income tax rate	18.20%	18.30%	(15.30%)