Basis of Presentation and Consolidation - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended			12 Months Ended
	Feb. 15, 2019	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 12, 2018
Summary Of Significant Policies [Line Items]
Minimum percentage of investment consolidated		50.00%
Maximum percentage of cost method investments		20.00%
Unfavorable Regulatory Action
Summary Of Significant Policies [Line Items]
Loss contingency imposed (as a percent)	42.16%
Incurred expense on loss contingency		$ 10,048
Loss from Catastrophes | Cost of Sales
Summary Of Significant Policies [Line Items]
Incurred expense on loss contingency				$ 870	$ 1,569	$ 12,583
Recovered insurance proceeds				$ 3,809	$ 7,300	$ 7,000
GRT Acquisition
Summary Of Significant Policies [Line Items]
Goodwill impairment charge			$ 33,827
TBR
Summary Of Significant Policies [Line Items]
Noncontrolling interest (as a percent)							35.00%
TBR | GRT Acquisition | Minimum
Summary Of Significant Policies [Line Items]
Investment in joint venture							$ 190,000
TBR | GRT Acquisition | Maximum
Summary Of Significant Policies [Line Items]
Investment in joint venture							$ 210,000