Fair Values of Financial Instruments (Fair Values and Carrying Amounts of Financial Instruments) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets
Fixed maturity securities, available for sale, fair value	$ 51,700,743	$ 51,580,490
Derivative instruments	874,741	1,355,989
Other investments	495,740	492,301
Coinsurance deposits (net of allowance for credit losses of $2,648 as of 2020 and $0 as of 2019)	4,886,705	5,115,013
Liabilities
Policy benefit reserves	60,109,669	61,893,945
Carrying Amount
Assets
Fixed maturity securities, available for sale, fair value	51,700,743	51,580,490
Mortgage loans on real estate	3,926,699	3,448,793
Derivative instruments	874,741	1,355,989
Other investments	495,740	492,301
Cash and cash equivalents	2,656,632	2,293,392
Coinsurance deposits (net of allowance for credit losses of $2,648 as of 2020 and $0 as of 2019)	4,886,705	5,115,013
Liabilities
Policy benefit reserves	59,750,209	61,540,992
Single premium immediate annuity (SPIA) benefit reserves	241,782	255,698
Notes payable	495,528	495,116
Subordinated debentures	78,037	157,265
Carrying Amount \| Interest Rate Caps
Assets
Interest rate derivative assets	0	6
Fair Value
Assets
Fixed maturity securities, available for sale, fair value	51,700,743	51,580,490
Mortgage loans on real estate	4,070,821	3,536,446
Derivative instruments	874,741	1,355,989
Other investments	495,740	492,301
Cash and cash equivalents	2,656,632	2,293,392
Coinsurance deposits (net of allowance for credit losses of $2,648 as of 2020 and $0 as of 2019)	4,480,027	4,635,926
Liabilities
Policy benefit reserves	51,872,229	51,800,247
Single premium immediate annuity (SPIA) benefit reserves	249,341	263,773
Notes payable	544,640	541,520
Subordinated debentures	81,451	168,357
Fair Value \| Interest Rate Caps
Assets
Interest rate derivative assets	$ 0	$ 6

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Fair value of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt.

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Amount, before effect of reinsurance, of present value of future benefit to be paid to or on behalf of policyholder and related expense less present value of future net premium receivable under insurance contract.

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Amount, after valuation allowance, recoverable under reinsurance contracts including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

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