Investments - Net Changes in Unrealized Gains (Losses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Gain (Loss) on Securities [Line Items]
Net unrealized gains (losses) on investments still held	$ (17,681)	$ (2,085)
Trading securities
Gain (Loss) on Securities [Line Items]
Trading securities	(13,033)	(8,089)
Equity securities
Gain (Loss) on Securities [Line Items]
Equity securities	(4,385)	5,118
Other investments
Gain (Loss) on Securities [Line Items]
Other investments	$ (263)	$ 886