Schedule II. Condensed Financial Information of Registrant (Condensed Statement of Cash Flows) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Condensed Financial Statements, Captions [Line Items]
Net income	$ 739,704	$ 744,959	$ 731,773
Other, net	26,588	109,616	66,602
Cash provided from (used for) operating activities	1,422,194	1,437,680	1,476,434
Cash provided from (used for) investing activities:
Net decrease (increase) in short-term investments	(44,976)	38,637	(69,497)
Cash provided from (used for) investing activities	(943,015)	(913,370)	(1,181,730)
Cash provided from (used for) financing activities:
Repayment of debt	(150,000)	(300,000)	(386,875)
Payment for debt issuance costs	(5,272)	(7,687)	(5,844)
Net issuance (repayment) of commercial paper	(46,289)	74,974	(34,445)
Issuance of stock	106,592	69,826	48,093
Acquisitions of treasury stock	(454,638)	(541,435)	(443,866)
Payment of dividends	(80,547)	(80,043)	(78,192)
Cash provided from (used for) financing activities	(492,453)	(523,603)	(274,057)
Net increase (decrease) in cash	396	(2,684)	18,914
Cash at beginning of year	92,163	94,847	75,933
Cash at end of year	92,559	92,163	94,847
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net income	739,704	744,959	731,773
Equity in earnings of affiliates	(808,303)	(788,768)	(760,329)
Cash dividends from subsidiaries	407,042	478,535	485,871
Other, net	26,444	58,617	21,129
Cash provided from (used for) operating activities	364,887	493,343	478,444
Cash provided from (used for) investing activities:
Net decrease (increase) in short-term investments	(15,001)	19,300	(15,899)
Investment in subsidiaries	(10,010)	(159,924)	(7,875)
Other long-term investments	(2,000)	(2,500)	0
Loaned money to affiliates	(846,002)	(1,049,932)	(1,008,860)
Repayments from affiliates	886,002	1,200,932	782,860
Cash provided from (used for) investing activities	12,989	7,876	(249,774)
Cash provided from (used for) financing activities:
Repayment of debt	(300,000)	(300,000)	(386,875)
Proceeds from issuance of debt	400,000	325,000	700,000
Payment for debt issuance costs	(5,272)	(7,687)	(5,844)
Net issuance (repayment) of commercial paper	(46,289)	74,974	(34,445)
Issuance of stock	111,970	69,826	48,093
Acquisitions of treasury stock	(454,638)	(541,435)	(443,866)
Borrowed money from affiliate	22,400	32,000	76,000
Repayments to affiliates	(22,400)	(32,000)	(79,500)
Payment of dividends	(103,817)	(103,313)	(101,462)
Cash provided from (used for) financing activities	(398,046)	(482,635)	(227,899)
Net increase (decrease) in cash	(20,170)	18,584	771
Cash at beginning of year	20,228	1,644	873
Cash at end of year	$ 58	$ 20,228	$ 1,644