New Accounting Standards - Balance Sheets (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Jan. 01, 2021	Dec. 31, 2020
Assets:
Other receivables	$ 594,421	$ 589,079
Deferred acquisition costs	5,654,438	5,535,697	$ 5,191,683	$ 4,587,547	$ 4,595,444
Liabilities:
Future policy benefits	18,896,574	18,040,042
Unearned and advance premium	271,517	253,140		243,369	61,728
Policy claims and other benefits payable	489,296	507,219		$ 473,524	$ 399,507
Current and deferred income taxes	427,608	434,649
Shareholders' equity:
Accumulated other comprehensive income	(2,961,093)	(2,790,313)
Retained earnings	$ 7,092,544	6,894,535
Previously Reported
Assets:
Other receivables		484,887
Deferred acquisition costs		5,249,907
Liabilities:
Future policy benefits		16,721,846
Unearned and advance premium		60,742
Policy claims and other benefits payable		430,027
Current and deferred income taxes		686,172
Shareholders' equity:
Accumulated other comprehensive income		(1,415,714)
Retained earnings		6,466,220
Revision of Prior Period, Adjustment
Assets:
Other receivables		104,192
Deferred acquisition costs		285,790
Liabilities:
Future policy benefits		1,318,196
Unearned and advance premium		192,398
Policy claims and other benefits payable		77,192
Current and deferred income taxes		(251,523)
Shareholders' equity:
Accumulated other comprehensive income		(1,374,599)
Retained earnings		$ 428,315