Investments - Components of Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Strategic investments:
Investments accounted for under the equity method	$ 16,707	$ 86,853
Investments held at fair value	9,198	1,814
Investments held at cost, less impairment	2,789	8,746
Total strategic investments	28,694	97,413
Other investments	2,285	1,530
Total investments	$ 30,979	$ 98,943