SCHEDULE III - SUPPLEMENTARY INSURANCE INFORMATION (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplementary insurance information
Deferred Policy Acquisition Costs and Value of Businesses Acquired	$ 3,023,154				$ 2,199,577				$ 3,023,154	$ 2,199,577	$ 2,019,829
Future Policy Benefits and Claims	41,901,552				30,957,592				41,901,552	30,957,592	30,511,085
Unearned Premiums	872,594				875,405				872,594	875,405	848,495
Stable Value Products, Annuity Contracts and Other Policyholders’ Funds	20,083,191				16,886,759				20,083,191	16,886,759	15,309,500
Net Premiums and Policy Fees	592,387	$ 608,847	$ 550,927	$ 543,743	516,965	$ 529,968	$ 525,241	$ 544,510	2,295,904	2,116,684	2,093,215
Net Investment Income									2,483,750	2,051,588	1,942,456
Benefits and Settlement Expenses									3,515,869	2,957,270	2,880,435
Amortization of deferred policy acquisition costs and value of business acquired									225,808	78,221	149,064
Other Operating Expenses									916,258	948,244	860,451
Premiums Written									161,624	176,900	154,450
Life Marketing
Supplementary insurance information
Deferred Policy Acquisition Costs and Value of Businesses Acquired	1,499,386				1,320,776				1,499,386	1,320,776	1,218,944
Future Policy Benefits and Claims	15,318,019				15,438,739				15,318,019	15,438,739	14,595,370
Unearned Premiums	98				107				98	107	119
Stable Value Products, Annuity Contracts and Other Policyholders’ Funds	422,037				424,204				422,037	424,204	426,422
Net Premiums and Policy Fees									1,043,228	1,011,911	972,247
Net Investment Income									551,781	553,999	525,495
Benefits and Settlement Expenses									1,412,001	1,319,138	1,267,844
Amortization of deferred policy acquisition costs and value of business acquired									116,917	120,753	130,708
Other Operating Expenses									197,346	178,792	177,498
Premiums Written									92	111	122
Acquisitions
Supplementary insurance information
Deferred Policy Acquisition Costs and Value of Businesses Acquired	458,976				74,862				458,976	74,862	106,532
Future Policy Benefits and Claims	25,427,730				14,323,713				25,427,730	14,323,713	14,693,744
Unearned Premiums	2,206				2,423				2,206	2,423	2,734
Stable Value Products, Annuity Contracts and Other Policyholders’ Funds	6,018,954				4,377,020				6,018,954	4,377,020	4,247,081
Net Premiums and Policy Fees									952,315	785,188	832,083
Net Investment Income									1,108,218	752,520	764,571
Benefits and Settlement Expenses									1,636,697	1,204,084	1,232,141
Amortization of deferred policy acquisition costs and value of business acquired									18,690	(6,939)	8,178
Other Operating Expenses									143,698	110,607	118,056
Premiums Written									13,750	15,964	18,818
Annuities
Supplementary insurance information
Deferred Policy Acquisition Costs and Value of Businesses Acquired	889,697				772,633				889,697	772,633	655,618
Future Policy Benefits and Claims	1,050,161				1,080,629				1,050,161	1,080,629	1,097,973
Unearned Premiums	0				0				0	0	0
Stable Value Products, Annuity Contracts and Other Policyholders’ Funds	8,324,931				7,308,354				8,324,931	7,308,354	7,059,060
Net Premiums and Policy Fees									148,033	152,701	146,458
Net Investment Income									340,685	321,844	322,608
Benefits and Settlement Expenses									226,704	216,629	214,100
Amortization of deferred policy acquisition costs and value of business acquired									24,274	(54,471)	(11,031)
Other Operating Expenses									151,054	149,181	140,409
Premiums Written									0	0	0
Stable Value Products
Supplementary insurance information
Deferred Policy Acquisition Costs and Value of Businesses Acquired	6,121				6,864				6,121	6,864	5,455
Future Policy Benefits and Claims	0				0				0	0	0
Unearned Premiums	0				0				0	0	0
Stable Value Products, Annuity Contracts and Other Policyholders’ Funds	5,234,731				4,698,371				5,234,731	4,698,371	3,501,636
Net Premiums and Policy Fees									0	0	0
Net Investment Income									217,778	186,576	107,010
Benefits and Settlement Expenses									109,747	74,578	41,736
Amortization of deferred policy acquisition costs and value of business acquired									3,201	2,354	1,176
Other Operating Expenses									2,798	4,407	3,033
Premiums Written									0	0	0
Asset Protection
Supplementary insurance information
Deferred Policy Acquisition Costs and Value of Businesses Acquired	168,974				24,442				168,974	24,442	33,280
Future Policy Benefits and Claims	52,636				55,847				52,636	55,847	60,790
Unearned Premiums	869,615				872,600				869,615	872,600	844,919
Stable Value Products, Annuity Contracts and Other Policyholders’ Funds	0				0				0	0	0
Net Premiums and Policy Fees									140,130	154,166	128,687
Net Investment Income									30,457	27,325	22,082
Benefits and Settlement Expenses									113,073	126,459	106,668
Amortization of deferred policy acquisition costs and value of business acquired									62,726	16,524	20,033
Other Operating Expenses									104,533	160,235	125,957
Premiums Written									135,596	148,093	121,821
Corporate and Other
Supplementary insurance information
Deferred Policy Acquisition Costs and Value of Businesses Acquired	0				0				0	0	0
Future Policy Benefits and Claims	53,006				58,664				53,006	58,664	63,208
Unearned Premiums	675				275				675	275	723
Stable Value Products, Annuity Contracts and Other Policyholders’ Funds	$ 82,538				$ 78,810				82,538	78,810	75,301
Net Premiums and Policy Fees									12,198	12,718	13,740
Net Investment Income									234,831	209,324	200,690
Benefits and Settlement Expenses									17,647	16,382	17,946
Amortization of deferred policy acquisition costs and value of business acquired									0	0	0
Other Operating Expenses									316,829	345,022	295,498
Premiums Written									$ 12,186	$ 12,732	$ 13,689