Exit and Termination Costs - Termination Costs Included in Accrued Liabilities in Consolidated Balance Sheet - (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Exit costs included in accrued liabilities in consolidated balance sheet
Balance at December 31, 2019			$ 4,692
Accrued severance costs	$ (148)	$ 2,180	1,447	$ 2,180
Accrued transportation contracts	10,445		10,445
Payments			(4,199)
Balance at June 30, 2020	$ 12,385		$ 12,385