CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash Flows from Operating Activities:
Net income	$ 304,604	$ 377,702
Change in operating assets and liabilities:
Accrued investment income	1,834	(34,676)
Premiums receivable and other reinsurance balances	(345,253)	(230,650)
Deferred policy acquisition costs	20,528	35,870
Reinsurance ceded receivable balances	18,245	(127,995)
Future policy benefits, other policy claims and benefits, and other reinsurance balances	598,015	745,799
Deferred income taxes	48,117	142,044
Other assets and other liabilities, net	(98,807)	(63,811)
Amortization of net investment premiums, discounts and other	(25,713)	(47,563)
Depreciation, Depletion and Amortization	21,554	13,869
Investment related (gains) losses, net	11,042	(116,818)
Other, net	29,422	(37,797)
Net cash provided by operating activities	583,588	655,974
Cash Flows from Investing Activities:
Sales of fixed maturity securities available-for-sale	3,836,575	4,288,713
Maturities of fixed maturity securities available-for-sale	328,097	313,530
Proceeds from Sale of Available-for-sale Securities, Equity	29,099	166,916
Payments to Acquire Debt Securities, Available-for-sale	3,880,733	5,311,818
Payments to Acquire Available-for-sale Securities, Equity	(11,930)	(32,299)
Payments to Acquire Mortgage Notes Receivable	(376,470)	(463,063)
Proceeds from Sale and Collection of Mortgage Notes Receivable	213,691	135,450
Proceeds from Collection of Policy Loans	24,793	26,658
Payments for (Proceeds from) Policy Loans	6,421	5,830
Increase (Decrease) in Funds Held under Reinsurance Agreements	42,761	6,910
Payments to Acquire Businesses, Net of Cash Acquired	(29,315)	0
Payments to Acquire Property, Plant, and Equipment	(14,573)	31,686
Change in short-term investments	(9,843)	22,671
Change in other invested assets	(160,824)	(55,379)
Net cash used in investing activities	(100,615)	(889,675)
Cash Flows from Financing Activities:
Dividends to stockholders	(64,370)	(52,815)
Proceeds from (Repayments of) Secured Debt	(53,102)	(23,761)
Repayments of Long-term Debt	(1,331)	(301,278)
Purchases of treasury stock	(165,069)	(10,578)
Exercise of stock options, net	1,252	2,527
Change in cash collateral for derivative positions and other arrangements	17,578	(7,046)
Deposits on universal life and other investment type policies and contracts	225,876	917,675
Withdrawals on universal life and other investment type policies and contracts	(329,899)	(402,528)
Net cash (used in) provided by financing activities	(369,065)	122,196
Effect of exchange rate changes on cash	(19,753)	34,137
Change in cash and cash equivalents	94,155	(77,368)
Cash and cash equivalents, beginning of period	1,303,524	1,200,718
Cash and cash equivalents, end of period	1,397,679	1,123,350
Supplemental disclosures of cash flow information:
Interest Paid, Excluding Capitalized Interest, Operating Activities	84,670	90,425
Income Taxes Paid, Net	59,397	26,447
Transfer to Investments	604,374	2,243,360
Noncash or Part Noncash Acquisition, Value of Assets Acquired	65,948	0
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed	$ 36,633	$ 0