Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities
Net income	$ 473,992	$ 671,460	$ 246,090
Adjustments to reconcile net income to net cash provided by operating activities:
Interest sensitive and index product benefits	2,681,406	1,543,270	1,287,576
Amortization of deferred sales inducements	152,692	438,164	88,585
Annuity product charges	(242,631)	(251,227)	(240,035)
Change in fair value of embedded derivatives	(358,302)	(1,286,787)	1,454,042
Change in traditional life and accident and health insurance reserves	40,090	8,694	(3,546)
Policy acquisition costs deferred	(307,857)	(255,154)	(422,516)
Amortization of deferred policy acquisition costs	268,328	649,554	87,717
Provision for depreciation and other amortization	5,527	5,199	4,068
Amortization of discounts and premiums on investments	19,861	57,437	25,846
Loss on extinguishment of debt	0	2,024	2,001
Realized gains/losses on investments	13,242	80,680	(6,962)
Realized gains/losses on investments			11,764
Change in fair value of derivatives	(1,348,704)	(34,668)	(906,201)
Distributions from equity method investments	12,409	1,968	2,753
Deferred income taxes	128,423	141,071	56,947
Share-based compensation	24,601	10,215	11,295
Change in accrued investment income	(47,015)	74,744	(4,097)
Change in income taxes recoverable/payable	(165,724)	(1,291)	26,966
Change in other assets	(4,464)	(849)	(5,607)
Change in other policy funds and contract claims	(19,809)	(21,865)	(21,971)
Change in collateral held for derivatives	17,423	(72,413)	1,190,656
Change in collateral held for securities lending	0	(495,039)	495,101
Change in funds withheld from reinsurers	3,124,740	0	0
Change in other liabilities	(221,726)	38,995	(28,607)
Other	(13,338)	804	(7,425)
Net cash provided by operating activities	4,233,164	1,304,986	3,351,402
Sales, maturities, or repayments of investments:
Fixed maturity securities - available for sale	4,490,736	8,291,316	3,266,821
Mortgage loans on real estate	862,666	378,812	294,356
Derivative instruments	2,260,959	860,520	657,885
Other investments	368,837	4,324	472,549
Acquisitions of investments:
Fixed maturity securities - available for sale	(9,206,733)	(2,429,114)	(5,509,314)
Mortgage loans on real estate	(2,386,712)	(1,121,756)	(799,037)
Real estate investments acquired	(335,767)	0	0
Derivative instruments	(748,061)	(730,333)	(823,077)
Other investments	(1,512,123)	(105,925)	(611,047)
Purchases of property, furniture and equipment	(18,109)	(13,240)	(4,022)
Net cash provided by (used in) investing activities	(6,224,307)	5,134,604	(3,054,886)
Financing activities
Receipts credited to annuity policyholder account balances	5,910,024	3,648,936	4,951,211
Coinsurance deposits	(3,187,332)	430,644	91,238
Return of annuity policyholder account balances	(5,145,193)	(4,040,054)	(3,584,960)
Repayment of subordinated debentures	0	(81,450)	(88,160)
Net proceeds from (repayments of) amounts due under repurchase agreements	0	0	(109,298)
Proceeds from issuance of common stock, net	4,854	338,061	1,691
Acquisition of treasury stock	(99,415)	(165,094)	0
Proceeds from issuance of preferred stock, net	0	290,260	388,893
Change in checks in excess of cash balance	(3,210)	3,611	29,169
Dividends paid on common stock	(31,450)	(28,859)	(27,304)
Dividends paid on preferred stock	(43,675)	(33,515)	0
Net cash provided by (used in) financing activities	(2,595,397)	362,540	1,652,480
Increase (decrease) in cash and cash equivalents	(4,586,540)	6,802,130	1,948,996
Cash and cash equivalents at beginning of year	9,095,522	2,293,392	344,396
Cash and cash equivalents at end of year	4,508,982	9,095,522	2,293,392
Cash paid during the year for interest:
Interest expense	30,000	31,427	42,879
Cash paid during the year for income taxes:
Income taxes	165,537	4,842	28,413
Non-cash operating activity:
Deferral of sales inducements	$ 95,160	$ 93,610	$ 177,941