CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash Flows from Operating Activities:
Net income	$ 605,803	$ 605,293
Change in operating assets and liabilities:
Accrued investment income	23,473	(63,321)
Premiums receivable and other reinsurance balances	(519,107)	(421,027)
Deferred policy acquisition costs	23,682	67,471
Reinsurance ceded receivable balances	37,468	(120,013)
Future policy benefits, other policy claims and benefits, and other reinsurance balances	920,492	982,164
Deferred income taxes	(8,136)	236,185
Other assets and other liabilities, net	(47,978)	78,848
Amortization of net investment premiums, discounts and other	(55,154)	(95,227)
Depreciation, Depletion and Amortization	32,153	21,384
Investment related (gains) losses, net	31,059	(139,471)
Other, net	56,408	(47,787)
Net cash provided by operating activities	1,100,163	1,104,499
Cash Flows from Investing Activities:
Sales of fixed maturity securities available-for-sale	6,314,968	6,364,236
Maturities of fixed maturity securities available-for-sale	461,764	385,993
Proceeds from Sale of Available-for-sale Securities, Equity	44,952	192,821
Payments to Acquire Debt Securities, Available-for-sale	6,041,665	7,450,749
Payments to Acquire Available-for-sale Securities, Equity	(12,578)	(60,790)
Payments to Acquire Mortgage Notes Receivable	(671,956)	(751,702)
Proceeds from Sale and Collection of Mortgage Notes Receivable	290,450	208,052
Proceeds from Collection of Policy Loans	43,995	93,286
Payments for (Proceeds from) Policy Loans	6,422	5,830
Increase (Decrease) in Funds Held under Reinsurance Agreements	61,969	12,597
Payments to Acquire Businesses, Net of Cash Acquired	31,441	0
Payments to Acquire Property, Plant, and Equipment	(20,478)	(33,242)
Change in short-term investments	34,856	65,664
Change in other invested assets	(313,464)	(51,476)
Net cash provided by (used in) investing activities	31,012	(1,056,334)
Cash Flows from Financing Activities:
Dividends to stockholders	(102,441)	(85,086)
Proceeds from (Repayments of) Secured Debt	(75,146)	(56,637)
Repayments of Long-term Debt	(2,007)	(301,927)
Purchases of treasury stock	(273,873)	(41,360)
Exercise of stock options, net	2,336	4,450
Change in cash collateral for derivative positions and other arrangements	(21,288)	(46,206)
Deposits on universal life and other investment type policies and contracts	320,871	1,007,563
Withdrawals on universal life and other investment type policies and contracts	(520,649)	(568,789)
Net cash used in financing activities	(672,197)	(87,992)
Effect of exchange rate changes on cash	(32,013)	43,699
Change in cash and cash equivalents	426,965	3,872
Cash and cash equivalents, beginning of period	1,303,524	1,200,718
Cash and cash equivalents, end of period	1,730,489	1,204,590
Supplemental disclosures of cash flow information:
Interest Paid, Excluding Capitalized Interest, Operating Activities	124,575	129,136
Income Taxes Paid, Net	99,554	27,385
Transfer to Investments	3,763,195	2,247,136
Noncash or Part Noncash Acquisition, Value of Assets Acquired	69,853	0
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed	$ (38,412)	$ 0