Reinsurance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Life insurance in-force
Written and earned direct	$ 97,954,580	$ 96,428,523
Reinsurance ceded	(11,995,685)	(11,401,557)
Reinsurance assumed	53,532,666	56,165,011
Net	$ 139,491,561	$ 141,191,977
Percentage of amount assumed to net	38.00%	40.00%
Premium income
Net	$ 439,731	$ 465,349	$ 445,550
Individual
Life insurance in-force
Written and earned direct	56,059,075	54,618,888
Reinsurance ceded	(10,881,048)	(10,568,467)
Reinsurance assumed	53,532,666	56,165,011
Net	$ 98,710,693	$ 100,215,432
Percentage of amount assumed to net	54.00%	56.00%
Group
Life insurance in-force
Written and earned direct	$ 41,895,505	$ 41,809,635
Reinsurance ceded	(1,114,637)	(833,090)
Reinsurance assumed	0	0
Net	$ 40,780,868	$ 40,976,545
Percentage of amount assumed to net	0.00%	0.00%
Life insurance
Premium income
Written and earned direct	$ 373,896	$ 392,654	368,442
Reinsurance ceded	(55,945)	(52,397)	(48,107)
Reinsurance assumed	119,684	123,175	124,798
Net	437,635	463,432	445,133
Annuities
Premium income
Written and earned direct	2,184	1,998	503
Reinsurance ceded	(88)	(81)	(86)
Net	2,096	1,917	417
Premium Income
Premium income
Written and earned direct	376,080	394,652	368,945
Reinsurance ceded	(56,033)	(52,478)	(48,193)
Reinsurance assumed	119,684	123,175	124,798
Net	$ 439,731	$ 465,349	$ 445,550