Condensed Consolidated Statements of Cash Flows - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net cash provided by operating activities	$ 504,175,000	$ 457,941,000
Proceeds from sales, maturities and redemptions of investments:
Fixed maturities, available-for-sale	3,132,414,000	4,056,220,000
Mortgage loans on real estate	209,888,000	128,908,000
Limited partnership interests, other corporation interests and other investments	4,745,000	7,642,000
Purchases of investments:
Fixed maturities, available-for-sale	(2,840,513,000)	(2,837,403,000)
Mortgage loans on real estate	(565,217,000)	(374,710,000)
Limited partnership interests, other corporation interests and other investments	(8,114,000)	(3,234,000)
Net change in short-term investments	(612,835,000)	(2,150,029,000)
Net change in policy loans	(9,037,000)	6,723,000
Purchases of furniture, equipment, and software	(21,710,000)	(20,652,000)
Net cash used in investing activities	(710,379,000)	(1,186,535,000)
Cash flows from financing activities:
Contract deposits	1,405,204,000	1,766,662,000
Contract withdrawals	(1,087,940,000)	(978,575,000)
Net change in due to/from parent and affiliates	(21,388,000)	1,067,000
Dividends paid	(137,301,000)	(104,831,000)
Capital contribution	76,429,000	0
Payments for and interest paid on financing element derivatives, net	(3,461,000)	(5,111,000)
Net change in commercial paper borrowings	(27,796,000)	6,298,000
Net change in book overdrafts	1,623,000	17,613,000
Employee taxes paid for withheld shares	(648,000)	(484,000)
Income tax benefit on share-based compensation	0	405,000
Net cash provided by financing activities	204,722,000	703,044,000
Net decrease in cash and cash equivalents	(1,482,000)	(25,550,000)
Cash and cash equivalents, beginning of year	18,321,000	34,362,000
Cash and cash equivalents, end of period	16,839,000	8,812,000
Net cash paid during the year for:
Income taxes	(10,449,000)	(16,391,000)
Interest	(12,931,000)	(18,798,000)
Non-cash investing and financing transactions during the years:
Share-based compensation expense	$ 925,000	$ 1,059,000