Investments Gain (Loss) on Marketable Equity Securities) (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments [Abstract]
Gain (loss) on marketable equity securities, net	$ 49,407	$ 17,404	$ 7,791	$ 24,066	$ (44,149)	$ 44,962	$ (2,554)	$ (14,102)	$ 98,668	$ (15,843)	$ 0
Less: Net (gains) losses in earnings from marketable equity securities sold									(2,810)	4,271
Net unrealized gains (losses) in earnings from marketable equity securities still held at the end of the year									$ 95,858	$ (11,572)