Investments - Net Changes in Unrealized Gains (Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments still held	$ 4,053	$ 12,590	$ 28,078
Trading securities
Gain (Loss) on Securities [Line Items]
Trading securities	(7,330)	10,583	16,346
Equity securities
Gain (Loss) on Securities [Line Items]
Equity securities	10,210	1,759	11,906
Other investments
Gain (Loss) on Securities [Line Items]
Other investments	$ 1,173	$ 248	$ (174)