Condensed Consolidated Statements of Earnings (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Premiums and other revenues:
Universal life and annuity contract charges	$ 40,363	$ 36,653	$ 78,262	$ 72,852
Traditional life premiums	5,218	4,904	9,082	8,987
Net investment income	129,687	78,181	310,501	227,739
Other revenues	5,990	5,866	12,132	11,521
Net realized investment gains (losses):
Total other-than-temporary impairment (“OTTI”) gains (losses)	(72)	(185)	310	(462)
Portion of OTTI (gains) losses recognized in other comprehensive income	(106)	(235)	(549)	(157)
Net OTTI losses recognized in earnings	(178)	(420)	(239)	(619)
Other net investment gains (losses)	1,779	2,425	4,153	3,791
Total net realized investment gains (losses)	1,601	2,005	3,914	3,172
Total condensed consolidated premiums and other revenues	182,859	127,609	413,891	324,271
Benefits and expenses:
Life and other policy benefits	18,450	13,857	31,140	27,535
Amortization of deferred policy acquisition costs	28,852	31,349	59,656	63,060
Universal life and annuity contract interest	71,438	26,004	211,738	127,547
Other operating expenses	24,843	22,452	46,767	42,470
Total benefits and expenses	143,583	93,662	349,301	260,612
Earnings before Federal income taxes	39,276	33,947	64,590	63,659
Federal income taxes	12,285	10,701	20,967	20,672
Net earnings	26,991	23,246	43,623	42,987
Common Class A [Member]
Benefits and expenses:
Net earnings	26,227	22,589	42,389	41,771
Basic earnings per share:
Earnings Per Share, Basic (in dollars per share)	$ 7.64	$ 6.58	$ 12.34	$ 12.16
Diluted earnings per share:
Earnings Per Share, Diluted (in dollars per share)	$ 7.62	$ 6.58	$ 12.32	$ 12.16
Common Class B [Member]
Benefits and expenses:
Net earnings	$ 764	$ 658	$ 1,234	$ 1,216
Basic earnings per share:
Earnings Per Share, Basic (in dollars per share)	$ 3.82	$ 3.29	$ 6.17	$ 6.08
Diluted earnings per share:
Earnings Per Share, Diluted (in dollars per share)	$ 3.82	$ 3.29	$ 6.17	$ 6.08