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Adjustment to the discount rate used to measure fair value for lack of ability to convert business interests into cash quickly.

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Amount of the effect of a change in accounting principle on diluted earnings per share.

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Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Significant Accounting Policies [Line Items]
Operating Leases, Future Minimum Payments Due		$ 226,475
Lower Limit
Significant Accounting Policies [Line Items]
Derivative, Term of Contract		1 year
Marketability discount		10.00%
Duration of the sale restrictions		3 months
Upper Limit
Significant Accounting Policies [Line Items]
Derivative, Term of Contract		5 years
Marketability discount		20.00%
Duration of the sale restrictions		6 months
Percentage of voting interest held by the company for investments accounted for under the equity method		5.00%	5.00%
Investments in limited partnerships \| Lower Limit
Significant Accounting Policies [Line Items]
Percentage of voting interest held by the company for investments accounted for under the equity method		5.00%
Investments in limited partnerships \| Upper Limit
Significant Accounting Policies [Line Items]
Percentage of ownership interest held by the company for investments accounted for under the cost method		5.00%
Privately Held Companies \| Lower Limit
Significant Accounting Policies [Line Items]
Percentage of voting interest held by the company for investments accounted for under the equity method		20.00%
Accounting Standards Update 2016-09 [Member]
Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income		$ 18,000
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Diluted Earnings Per Share		$ 0.34
Scenario, Forecast [Member] \| Accounting Standards Update 2016-09
Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 8,000
Scenario, Forecast [Member] \| Accounting Standards Update 2016-02 [Member]
Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	226,000
Scenario, Forecast [Member] \| Accounting Standards Update 2018-02 [Domain]
Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	0
Other investments \| China Joint Venture investment \| Equity method accounting
Significant Accounting Policies [Line Items]
Ownership percentage of each Fund		50.00%	50.00%
Venture capital and private equity fund investments \| Scenario, Forecast [Member] \| Accounting Standards Update 2016-01 [Member] \| Cost method accounting
Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	100,000
Equity securities \| Scenario, Forecast [Member] \| Accounting Standards Update 2016-01 [Member]
Significant Accounting Policies [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 40,000