General and Summary of Significant Accounting Policies Investments (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	$ 24,640
Available-for-sale Securities, Gross Unrealized Gain (Loss)	0
Available-for-sale Securities	$ 24,640
Investment Contract Settlement Date Range End	Jul. 22, 2020
Investment Contract Settlement Date Range Start	Jan. 15, 2018
Long-term Investments [Domain]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	$ 14,579
Available-for-sale Securities, Gross Unrealized Gain (Loss)	0
Available-for-sale Securities	14,579
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	10,061
Available-for-sale Securities, Gross Unrealized Gain (Loss)	0
Available-for-sale Securities	$ 10,061