Reinsurance (Income Statement Reinsurance Results) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Premiums
Direct	$ 433,616	$ 408,518	$ 851,609	$ 799,698
Assumed	65	1	131	149
Ceded	(416,604)	(1,260,611)	(828,906)	(1,634,024)
Net premiums	17,077	(852,092)	22,834	(834,177)
Policy charges and fee income
Direct	690,307	551,741	1,471,868	1,284,631
Assumed	115,955	109,910	232,294	304,223
Ceded	(938,787)	(602,720)	(1,708,685)	(1,003,361)
Net policy charges and fee income	(132,525)	58,931	(4,523)	585,493
Net investment income
Direct	91,993	79,518	182,394	185,656
Assumed	368	351	728	695
Ceded	(1,320)	(1,250)	(2,466)	(2,280)
Net investment income	91,041	78,619	180,656	184,071
Asset administration fees
Direct	83,994	76,600	164,993	149,391
Assumed	0	0	0	0
Ceded	(79,604)	(72,996)	(156,416)	(72,996)
Net asset administration fees	4,390	3,604	8,577	76,395
Other income
Direct	14,501	12,077	29,939	23,772
Assumed	(342)	425	209	384
Ceded	(11)	0	(23)	0
Amortization of reinsurance income	0	(21,101)	0	(19,233)
Net other income	14,148	(8,599)	30,125	4,923
Realized investment gains (losses), net
Direct	(1,569,801)	(1,228,076)	(947,675)	(2,762,428)
Assumed	0	39	0	0
Ceded	1,846,391	2,088,499	1,191,686	3,678,041
Realized investment gains (losses), net	276,590	860,462	244,011	915,613
Policyholders’ benefits (including change in reserves)
Direct	548,727	178,623	1,234,222	796,766
Assumed	118,499	211,699	247,636	472,575
Ceded	(871,243)	(862,932)	(1,614,388)	(1,641,221)
Net policyholders’ benefits (including change in reserves)	(204,017)	(472,610)	(132,530)	(371,880)
Interest credited to policyholders’ account balances
Direct	10,431	105,629	109,348	319,111
Assumed	33,895	31,583	67,829	65,418
Ceded	1,641	(109,236)	(86,450)	(170,122)
Net interest credited to policyholders’ account balances	45,967	27,976	90,727	214,407
Reinsurance expense allowances and general and administrative expenses, net of capitalization and amortization	(104,219)	(480,948)	(466,455)	(573,016)
Unaffiliated activity
Premiums
Assumed	100	0	100	100
Policy charges and fee income
Ceded	400	300	1,000	500
Other income
Assumed	(300)	400	200	400
Realized investment gains (losses), net
Ceded	31,000	21,000	22,000	46,000
Policyholders’ benefits (including change in reserves)
Assumed	0	0	300	200
Ceded	$ (3,000)	$ (3,000)	$ (6,000)	$ (5,000)