Investments Fair Value Inputs, Assets, Quantitative Information (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Equity Securities without Readily Determinable Fair Value
Other investments, cost	$ 968,690
Available-for-sale Securities	1,001,970	$ 943,623
Limited Partner
Equity Securities without Readily Determinable Fair Value
Other investments, cost	7,568	7,988
Unrealized gain	2,236	225
Fair value	9,753	8,213
Unrealized loss	51	0
Certificates of Deposit
Equity Securities without Readily Determinable Fair Value
Certificates of Deposit, at Carrying Value	300	300
Other investments, cost	300	300
Unrealized gain	0	0
Unrealized loss	0	0
Short-term Investments
Equity Securities without Readily Determinable Fair Value
Unrealized gain	0
Fair value	199
Unrealized loss	0
Available-for-sale Securities	199
Other Long-term Investments
Equity Securities without Readily Determinable Fair Value
Other investments, cost	8,067	8,288
Unrealized gain	2,236	225
Unrealized loss	51	0
Total other investments	$ 10,252	$ 8,513