Discontinued Operations - Changes in Future Remaining Lease Obligations Discontinued Operations (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Discontinued Operations And Disposal Groups [Abstract]
Balance, Beginning of Period		$ 3,109	$ 9,698	$ 6,301	$ 14,474
Charges Incurred	[1]		251	3	769
Net Cash Payments		(1,150)	(1,538)	(4,345)	(6,832)
Balance, End of Period		$ 1,959	$ 8,411	$ 1,959	$ 8,411

[1] Includes subsequent adjustments for accretion, revised estimates and variances between estimated and actual charges, net of any reversals for terminated lease obligations.