Exit and Termination Costs - Exit and Termination Costs Included in Accrued Liabilities in Consolidated Balance Sheet - (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Exit costs included in accrued liabilities in consolidated balance sheet
Accrued severance costs		$ 509	$ 1,595
Exit Costs
Exit costs included in accrued liabilities in consolidated balance sheet
Beginning balance	[1]	493,543
Accrued severance costs	[1]	0
Accretion of discount	[1]	13,205
Payments	[1]	(25,848)
Ending balance	[1]	480,900
Termination Costs
Exit costs included in accrued liabilities in consolidated balance sheet
Beginning balance		1,454
Accrued severance costs		509
Accretion of discount		0
Payments		(1,432)
Ending balance		$ 531

[1] Includes the divestiture contract obligation and the capacity release obligation.