Long-Term Investments (Investments) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($) investment	Dec. 31, 2018 USD ($)
Long-term Investments [Abstract]
Equity securities at fair value that qualify for the NAV practical expedient	$ 53,175	$ 54,628
Equity-method investments	10,639	11,631
Long-term investments	$ 63,814	$ 66,259
Number of investments redeemed that qualify for the NAV practical expedient | investment	1
In-transit redemptions recorded from proceeds from investments redeemed that qualify for NAV practical expedient	$ 4,271