Accumulated Other Comprehensive Income - Changes in AOCI (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Changes in AOCI by component
Beginning balance	$ 6,835,917	$ 6,433,892
Ending balance	6,752,473	6,647,968
Cumulative Unrealized Gain (Loss) on Available-for- Sale Securities
Changes in AOCI by component
Beginning balance	20,955	40,953
OCI before reclassifications	0	(5,284)
Amounts reclassified from AOCI	(1,104)	0
Net period OCI	(1,104)	(5,284)
Ending balance	19,851	35,669
Accumulated Other Comprehensive Income
Changes in AOCI by component
Beginning balance	20,955	40,953
Ending balance	$ 19,851	$ 35,669