Investment Securities - U.S. Treasury Securities (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
US Treasury Bill #1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Face Value	$ 225,000
Unamortized Discount, net	8
Amortized Cost	224,992
Unrealized Loss	0
Debt securities, available-for-sale at fair value	$ 224,992
Net Effective Yield (as a percent)	0.10%
US Treasury Bill #2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Face Value	$ 125,000
Unamortized Discount, net	0
Amortized Cost	125,000
Unrealized Loss	0
Debt securities, available-for-sale at fair value	$ 125,000
Net Effective Yield (as a percent)	0.01%
U.S. Treasury Bills
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Face Value		$ 250,000
Unamortized Discount, net		0
Amortized Cost		250,000
Unrealized Loss		(1)
Debt securities, available-for-sale at fair value	$ 349,992	$ 249,999
Net Effective Yield (as a percent)		0.023%