Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net income	$ 317,369	$ 128,742	$ 238,114
Adjustments to reconcile net income to net cash provided by operating activities:
Losses allocated to participating policyholders	(1,041)	(804)	(580)
Amortization of premiums (accretion of discounts) on investments, net	(42,022)	(20,751)	(28,495)
Net realized (gains) losses on investments	(64,323)	(38,517)	(126,938)
Net proceeds (purchases) of trading securities	11,478	23,677	(220,646)
Interest credited to contractholders	571,860	507,987	515,356
Depreciation and amortization	76,461	81,061	82,595
Deferral of acquisition costs	(110,843)	(80,486)	(94,826)
Deferred income taxes	75,044	(24,087)	45,371
Amortization of low-income housing partnerships	21,713	31,918	39,621
Other, net	(4,984)	2,432	(2,681)
Changes in assets and liabilities:
Policy benefit liabilities	(151,096)	(49,980)	(192,755)
Reinsurance receivable	(18,054)	12,013	(15,893)
Investment income due and accrued	(8,951)	(12,448)	(8,654)
Other assets	(5,705)	(106,923)	(98,042)
Other liabilities	(6,568)	78,829	(37,444)
Net cash provided by operating activities	660,338	532,663	94,103
Proceeds from sales, maturities and redemptions of investments:
Fixed maturities, available-for-sale	4,124,159	4,022,064	4,308,965
Mortgage loans on real estate	384,306	289,531	172,950
Limited partnership interests, other corporation interests and other investments	7,555	22,200	12,530
Purchases of investments:
Fixed maturities, available-for-sale	(5,174,996)	(5,012,792)	(5,284,686)
Mortgage loans on real estate	(609,008)	(562,940)	(524,396)
Limited partnership interests, other corporation interests and other investments	(2,983)	(3,706)	(5,577)
Net change in short-term investments	22,096	(27,955)	81,058
Policy loans, net	(11,169)	(4,370)	4,983
Acquisition payment	(28,356)	0	0
Purchases of furniture, equipment and software	(35,537)	(20,618)	(23,525)
Net cash used in investing activities	(1,323,933)	(1,298,586)	(1,257,698)
Cash flows from financing activities:
Contract deposits	2,709,043	2,601,820	2,881,112
Contract withdrawals	(1,757,936)	(1,780,048)	(1,636,066)
Change in due to/from parent and affiliates	49,337	(14,724)	37,598
Dividends paid	(316,401)	(102,436)	(184,401)
Proceeds from financing element derivatives	5,516	51,832	64,354
Payments for and interest (paid) received on financing element derivatives, net	(8,392)	(9,756)	4,470
Net commercial paper borrowings	(401)	1,003	451
Change in book overdrafts	(12,052)	13,840	(609)
Income tax benefit of stock option exercises	165	496	480
Net cash provided by financing activities	668,879	762,027	1,167,389
Net increase (decrease) in cash	5,284	(3,896)	3,794
Cash, beginning of year	7,491	11,387	7,593
Cash, end of year	12,775	7,491	11,387
Net cash received (paid) during the year for:
Income taxes	46,453	(10,327)	53,281
Interest	(37,284)	(37,329)	(37,387)
Non-cash investing and financing transactions during the years:
Contingent consideration (See Note 2)	(32,209)	0	0
Share-based compensation expense	(3,384)	(2,578)	(2,314)
Fair value of assets acquired in settlement of fixed maturity investments	0	0	(1,125)
Assets received from limited partnership investment distribution	0	(5,119)	0
Fixed maturity investments, available-for-sale acquired in reinsurance termination (See Note 4)	0	(44,104)	0
Policy loans acquired in reinsurance termination (See Note 4)	0	(6,468)	0
Fixed maturity investments, available-for-sale acquired in mortgage transfer (See Note 4)	$ 0	$ (28,959)	$ 0