Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Statement of Cash Flows [Abstract]
Cash provided from operations	$ 729,892	$ 644,398
Long-term investments sold or matured:
Fixed maturities available for sale—sold	26,330	56,447
Fixed maturities available for sale—matured, called, and repaid	342,796	217,929
Equity securities	0	700
Other long-term investments	2,452	70
Total long-term investments sold or matured	371,578	275,146
Long-term investments acquired:
Fixed maturities	(730,145)	(499,950)
Other long-term investments	(1,906)	0
Total long-term investments acquired	(732,051)	(499,950)
Net increase in policy loans	(13,933)	(16,112)
Net (increase) decrease in short-term investments	(47,781)	(2,207)
Disposition of properties	0	54
Additions to properties	(30,663)	(14,482)
Investment in low-income housing interests	(27,078)	(39,279)
Cash used for investment activities	(479,928)	(296,830)
Cash provided from (used for) financing activities:
Proceeds from exercise of stock options	32,519	39,557
Net borrowings (repayments) of commercial paper	130,215	61,352
Excess tax benefit from stock option exercises	15,679	12,484
Acquisition of treasury stock	(330,066)	(342,084)
Cash dividends paid to shareholders	(50,217)	(48,628)
Net receipts (withdrawals) from deposit-type products	(69,188)	(49,431)
Cash provided by (used for) financing activities	(271,058)	(326,750)
Effect of foreign exchange rate changes on cash	14,560	9,237
Net (decrease) increase in cash	(6,534)	30,055
Cash at beginning of year	66,019	36,943
Cash at end of period	$ 59,485	$ 66,998