Reinsurance (Reinsurance Recoverable by Counterparty) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	$ 41,060,869	$ 38,709,651
PAR U
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	18,857,410	15,722,061
PURC
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	0	7,565,968
PARCC
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	2,212,090	2,304,270
GUL Re
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	0	3,211,899
PAR Term
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	2,048,613	2,101,004
Prudential Insurance
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	4,039,611	1,311,525
Term Re
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	2,040,735	2,080,564
Lotus Re
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	2,062,495	2,051,831
DART
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	779,290	744,043
PURE
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	7,445,335	0
Unaffiliated activity
Effects of Reinsurance [Line Items]
Total reinsurance recoverables	$ 1,575,290	$ 1,616,486