Accumulated Other Comprehensive Income - Changes in AOCI (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Changes in AOCI by component
Beginning balance	$ 6,433,892	$ 4,862,576
Ending balance	6,647,968	4,854,785
Cumulative Unrealized Gain (Loss) on Available-for- Sale Securities
Changes in AOCI by component
Beginning balance	40,953	44,057
OCI before reclassifications	0	(2,403)
Amounts reclassified from AOCI	(5,284)	0
Net period OCI	(5,284)	(2,403)
Ending balance	35,669	41,654
Foreign Currency Translation
Changes in AOCI by component
Beginning balance	0	(64)
OCI before reclassifications	0	0
Amounts reclassified from AOCI	0	64
Net period OCI	0	64
Ending balance	0	0
Accumulated Other Comprehensive Income
Changes in AOCI by component
Beginning balance	40,953	43,993
OCI before reclassifications	0	(2,403)
Amounts reclassified from AOCI	(5,284)	64
Net period OCI	(5,284)	(2,339)
Ending balance	$ 35,669	$ 41,654