Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015
Statement of Cash Flows [Abstract]
Cash provided from operating activities		$ 971,926	$ 729,892
Investments sold or matured:
Fixed maturities available for sale—sold		75,299	26,330
Fixed maturities available for sale—matured, called, and repaid		178,873	342,796
Other long-term investments		466	2,452
Total long-term investments sold or matured		254,638	371,578
Acquisition of investments:
Fixed maturities—available for sale		(910,090)	(730,145)
Other long-term investments		(20,404)	(1,906)
Total investments acquired		(930,494)	(732,051)
Net (increase) in policy loans		(6,623)	(13,933)
Net (increase) decrease in short-term investments		(11,138)	(47,781)
Net change in payable or receivable for securities		94	0
Additions to property and equipment		(10,138)	(30,663)
Sales of other assets		767	0
Investment in low-income housing interests		(16,126)	(27,078)
Cash from (used for) investing activities		(719,020)	(479,928)
Cash provided from (used for) financing activities:
Issuance of common stock		47,053	32,519
Cash dividends paid to shareholders		(50,258)	(50,217)
Repayment of 6.375% Notes		(250,000)	0
Issuance of Term Loan		100,000	0
Issuance of 6.125% Junior Subordinated Debentures		300,000	0
Issue expenses of debt offering		(9,638)	0
Net borrowing (repayment) of commercial paper		25,266	130,215
Excess tax benefit from stock option exercises	[1]	0	15,679
Acquisition of treasury stock		(311,356)	(330,066)
Net receipts (payments) from deposit-type product		(57,188)	(69,188)
Cash provided from (used for) financing activities		(206,121)	(271,058)
Effect of foreign exchange rate changes on cash		(3,268)	14,560
Net increase (decrease) in cash		43,517	(6,534)
Cash at beginning of year		61,383	66,019
Cash at end of period		$ 104,900	$ 59,485

[1] Due to the prospective adoption of ASU 2016-09, the excess tax benefits from stock option exercises of $14 million at September 30, 2016 were presented as a component of operating activities in the same manner as other cash flows related to income taxes. The 2015 balance of $16 million, under the previous guidance, remains in the financing activities section. See further discussion at Note 2—New Accounting Standards.