Fair Values of Financial Instruments (Fair Values and Carrying Amounts of Financial Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets
Fixed maturity securities, available for sale, fair value	$ 46,659,256	$ 47,538,893
Derivative instruments	1,459,965	1,310,954
Other investments	962,305	590,078
Coinsurance deposits (net of allowance for credit losses of $1,779 as of 2021 and $1,888 as of 2020)	4,441,950	4,844,927
Liabilities
Policy benefit reserves	64,555,597	62,352,882
Carrying Amount
Assets
Fixed maturity securities, available for sale, fair value	46,659,256	47,538,893
Mortgage loans on real estate	4,299,945	4,165,489
Real estate investments	258,237	0
Derivative instruments	1,459,965	1,310,954
Other investments	962,305	590,078
Cash and cash equivalents	11,524,265	9,095,522
Coinsurance deposits (net of allowance for credit losses of $1,779 as of 2021 and $1,888 as of 2020)	4,441,950	4,844,927
Liabilities
Policy benefit reserves	64,182,610	61,406,599
Single premium immediate annuity (SPIA) benefit reserves	233,331	240,226
Notes payable	495,955	495,668
Subordinated debentures	78,264	78,112
Fair Value
Assets
Fixed maturity securities, available for sale, fair value	46,659,256	47,538,893
Mortgage loans on real estate	4,457,553	4,327,885
Real estate investments	258,237	0
Derivative instruments	1,459,965	1,310,954
Other investments	962,305	590,078
Cash and cash equivalents	11,524,265	9,095,522
Coinsurance deposits (net of allowance for credit losses of $1,779 as of 2021 and $1,888 as of 2020)	4,077,954	4,411,051
Liabilities
Policy benefit reserves	55,231,714	52,928,174
Single premium immediate annuity (SPIA) benefit reserves	240,541	247,679
Notes payable	565,760	567,345
Subordinated debentures	$ 86,214	$ 87,951