Consolidated Statements of Operations - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Premiums and other considerations		$ 36,048	$ 32,623	$ 45,347
Annuity product charges		136,168	118,990	103,591
Net investment income		1,692,192	1,531,667	1,383,927
Change in fair value of derivatives		(336,146)	504,825	1,076,015
Net realized gains (losses) on investments, excluding other than temporary impairment (OTTI) losses		10,211	(4,003)	40,561
OTTI losses on investments:
Total OTTI losses		(25,547)	0	(4,964)
Portion of OTTI losses recognized in (from) other comprehensive income		6,011	(2,627)	(1,270)
Net OTTI losses recognized in operations		(19,536)	(2,627)	(6,234)
Loss on extinguishment of debt		0	(12,502)	(32,515)
Total revenues		1,518,937	2,168,973	2,610,692
Benefits and expenses:
Insurance policy benefits and change in future policy benefits		45,458	41,815	53,071
Interest sensitive and index product benefits		968,053	1,473,700	1,272,867
Amortization of deferred sales inducements		209,390	131,419	253,113
Change in fair value of embedded derivatives		(464,698)	32,321	133,968
Interest expense on notes payable		28,849	36,370	38,870
Interest expense on subordinated debentures		12,239	12,122	12,088
Amortization of deferred policy acquisition costs		286,114	163,578	365,468
Other operating costs and expenses		96,218	81,584	91,915
Total benefits and expenses		1,181,623	1,972,909	2,221,360
Income before income taxes		337,314	196,064	389,332
Income tax expense		117,484	70,041	136,049
Net income		$ 219,830	$ 126,023	$ 253,283
Earnings per common share		$ 2.78	$ 1.69	$ 3.86
Earnings per common share - assuming dilution		$ 2.72	$ 1.58	$ 3.38
Weighted average common shares outstanding: earnings per common share	[1]	78,936,828	74,431,087	65,543,895
Weighted average common shares outstanding: earnings per common share - assuming dilution		80,960,568	79,893,600	75,040,646

[1] Weighted average common shares outstanding include shares vested under the NMO Deferred Compensation Plan and exclude unallocated shares held by the ESOP.