Stock Plans: (Activity for Performance Share Units) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Performance Shares
Number of Shares
Beginning balance (in shares)	1,350,160	1,427,280	1,507,190
Granted (in shares)	396,400	543,560	482,360
Vested (in shares)	(686,052)	(916,452)	(902,232)
Adjustments for performance achievement (in shares)	282,492	374,402	400,992
Forfeited (in shares)	(38,620)	(78,630)	(61,030)
Ending balance (in shares)	1,304,380	1,350,160	1,427,280
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Total grant date fair value of PSU awards, granted	$ 68	$ 48	$ 55
Total grant date fair value of PSU awards, vested	(84)	(86)	(83)
Total grant date fair value of PSU awards, adjustments for performance achievement	36	36	37
Total grant date fair value of PSU awards, forfeited	(4)	(8)	(7)
Total fair value of PSU awards that vested	$ (102)	$ (83)	$ (91)
Performance Share Units, Other Performance Factors
Weighted- Average Grant Date Fair Value Per Share
Beginning balance (in dollars per share)	$ 98.00	$ 95.45	$ 90.31
Granted (in dollars per share)	145.35	89.01	102.02
Vested (in dollars per share)	104.97	82.28	85.99
Adjustments for performance achievement (in dollars per share)	104.97	82.17	85.99
Forfeited (in dollars per share)	105.55	97.42	98.24
Ending balance (in dollars per share)	110.02	98.00	95.45
Performance Share Units, TSR Performance Factor
Weighted- Average Grant Date Fair Value Per Share
Beginning balance (in dollars per share)	118.55	126.86	115.45
Granted (in dollars per share)	213.72	85.72	133.54
Vested (in dollars per share)	143.64	107.69	98.45
Adjustments for performance achievement (in dollars per share)	143.64	107.70	98.45
Forfeited (in dollars per share)	127.27	117.24	131.39
Ending balance (in dollars per share)	$ 139.46	$ 118.55	$ 126.86