Recently Adopted Accounting Standards and Recently Issued Accounting Pronouncements - Additional Information (Detail) $ / shares in Units, $ in Thousands			3 Months Ended		6 Months Ended	12 Months Ended
	Jan. 01, 2019 USD ($)	Jan. 01, 2018 USD ($)	Sep. 30, 2018 USD ($)	Mar. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) Asset	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Investment impairment charges						$ (4,678)
Prepaid income taxes					$ 8,600
Number of assets transferred | Asset					2
Increase (decrease) in net cash from operating activities						49,918	$ 38,972	$ 59,076
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 other long term assets				$ 1,600
Impact on remeasurement of equity investments per share before taxes recorded within other income | $ / shares				$ 0.09
Investment impairment charges			$ 4,400
ASU 2016-16 [Member]
Summary Of Significant Accounting Policies [Line Items]
New accounting standard update, reduction in prepaid income taxes		$ 8,600
New accounting standard update, increase in deferred tax assets		6,700
Cumulative-effect adjustment to retained earnings		$ (1,900)				(1,896)
ASU 2016-18 [Member]
Summary Of Significant Accounting Policies [Line Items]
Increase (decrease) in net cash from operating activities						2,500	$ (14,400)	$ 14,400
ASU 2017-01 [Member]
Summary Of Significant Accounting Policies [Line Items]
Assets Acquired Not Meeting The Definition of a Business						$ 3,400
ASU 2016-02 [Member] | Subsequent Event [Member]
Summary Of Significant Accounting Policies [Line Items]
Operating leases assets and liabilities expected to be recognized	$ 20,000
ASU 2018-02 [Member] | Scenario, Forecast [Member]
Summary Of Significant Accounting Policies [Line Items]
Increase to accumulated other comprehensive income and a decrease in retained earnings	$ 900