Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015
Cash provided from operating activities		$ 604,935	$ 454,121
Investments sold or matured:
Fixed maturities available for sale—sold		51,299	14,287
Fixed maturities available for sale—matured, called, and repaid		92,475	213,989
Other long-term investments		1,394	431
Total long-term investments sold or matured		145,168	228,707
Acquisition of investments:
Fixed maturities—available for sale		(651,267)	(541,875)
Other long-term investments		(21,762)	(1,886)
Total investments acquired		(673,029)	(543,761)
Net (increase) in policy loans		(9,093)	(7,844)
Net (increase) decrease in short-term investments		6,185	(12,813)
Net change in payable or receivable for securities		(711)	4,980
Additions to property and equipment		(6,740)	(13,949)
Investment in low-income housing interests		(9,260)	(11,954)
Cash from (used for) investing activities		(547,480)	(356,634)
Cash provided from (used for) financing activities:
Issuance of common stock		25,286	21,507
Cash dividends paid to shareholders		(33,478)	(33,306)
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		45,010	148,970
Excess tax benefit from stock option exercises	[1]	0	10,989
Acquisition of treasury stock		(202,975)	(211,567)
Net receipts (payments) from deposit-type product		(38,193)	(42,815)
Cash provided from (used for) financing activities		(63,988)	(106,222)
Effect of foreign exchange rate changes on cash		(5,172)	5,565
Net increase (decrease) in cash		(11,705)	(3,170)
Cash at beginning of year		61,383	66,019
Cash at end of period		49,678	$ 62,849
New Accounting Pronouncement, Early Adoption, Effect [Member]
Cash provided from (used for) financing activities:
Excess tax benefit from stock option exercises		$ 7,000

[1] Due to the prospective adoption of ASU 2016-09, the excess tax benefits from stock option exercises of $7 million at June 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 $11 million, under the previous guidance, remains in the financing activities section. See further discussion at Note 2—New Accounting Standards.