Recently Adopted Accounting Standards and Recently Issued Accounting Pronouncements - Additional Information (Detail) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended	9 Months Ended
	Jan. 01, 2018 USD ($)	Sep. 30, 2018 USD ($)	Mar. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) Asset	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Jan. 01, 2019 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Investment impairment charges		$ (4,449)			$ (4,678)
Prepaid income taxes				$ 8,600
Number of assets transferred | Asset				2
Increase (decrease) in net cash from operating activities					28,829	$ 9,125
ASU 2016-01 and 2018-03 [Member]
Summary Of Significant Accounting Policies [Line Items]
Impact on remeasurement of equity investments recorded within other current assets or long term assets			$ 1,600
Impact on remeasurement of equity investments per share before taxes recorded within other income (expense) | $ / shares			$ 0.09
Investment impairment charges		4,400
ASU 2016-16, as Amended [Member]
Summary Of Significant Accounting Policies [Line Items]
Cumulative-effect adjustment to retained earnings	$ 1,900
ASU 2016-18 [Member]
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in net cash from operating activities					$ 2,500	$ (14,400)
ASU 2017-01 [Member]
Summary Of Significant Accounting Policies [Line Items]
Assets Acquired Not Meeting The Definition of a Business		$ 700	$ 1,900
ASU 2016-02 [Member] | Scenario, Forecast [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Operating leases assets and liabilities expected to be recognized							$ 12,000