Debt (Tables)

6 Months Ended

Jun. 30, 2024

Debt Disclosure [Abstract]

Debt Table

Debt at each of the balance sheet periods consisted of:

	June 30, 2024				June 30, 2023				December 31, 2023
(millions)	Carrying Value		Fair Value		Carrying Value		Fair Value		Carrying Value		Fair Value
2.45% Senior Notes due 2027 (issued: $500.0, August 2016)	$	498.8	$	468.8	$	498.4	$	459.4	$	498.6	$	468.9
2.50% Senior Notes due 2027 (issued: $500.0, March 2022)	498.4		468.0		497.8		458.4		498.1		469.1
6 5/8% Senior Notes due 2029 (issued: $300.0, March 1999)	298.0		320.9		297.6		324.2		297.8		328.7
4.00% Senior Notes due 2029 (issued: $550.0, October 2018)	547.2		526.7		546.7		526.4		546.9		542.6
3.20% Senior Notes due 2030 (issued: $500.0, March 2020)	497.5		455.4		497.1		449.2		497.3		462.2
3.00% Senior Notes due 2032 (issued: $500.0, March 2022)	496.5		433.7		496.1		434.5		496.3		446.0
6.25% Senior Notes due 2032 (issued: $400.0, November 2002)	396.8		428.1		396.6		432.0		396.7		445.6
4.95% Senior Notes due 2033 (issued: $500.0, May 2023)	496.6		494.6		496.3		489.9		496.4		513.0
4.35% Senior Notes due 2044 (issued: $350.0, April 2014)	347.0		301.1		346.9		304.0		347.0		314.2
3.70% Senior Notes due 2045 (issued: $400.0, January 2015)	395.9		309.8		395.8		313.6		395.9		325.1
4.125% Senior Notes due 2047 (issued: $850.0, April 2017)	842.4		698.7		842.2		727.0		842.3		756.2
4.20% Senior Notes due 2048 (issued: $600.0, March 2018)	590.7		493.9		590.5		510.3		590.6		534.1
3.95% Senior Notes due 2050 (issued: $500.0, March 2020)	491.2		392.4		491.0		408.4		491.1		422.3
3.70% Senior Notes due 2052 (issued: $500.0, March 2022)	493.7		373.4		493.5		386.7		493.6		403.3
Total	$	6,890.7	$	6,165.5	$	6,886.5	$	6,224.0	$	6,888.6	$	6,431.3