Employee Benefits - Master Trust PBOP Fair Value Hierarchy (Details) - PBOP - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Other liabilities
Defined Contribution Plan Disclosure [Line Items]
Total liabilities	$ (0.7)	$ (18.0)
Short-term investments
Defined Contribution Plan Disclosure [Line Items]
Total assets	6.4	1.6
Other assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	1.6	15.7
Asset-backed securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	0.4	0.5
Corporate bonds
Defined Contribution Plan Disclosure [Line Items]
Total assets	45.1	47.8
Tax-exempt securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	32.0	34.9
Total assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	85.5	100.5
Level 1 | Other liabilities
Defined Contribution Plan Disclosure [Line Items]
Total liabilities	(0.7)	(18.0)
Level 2 | Other liabilities
Defined Contribution Plan Disclosure [Line Items]
Total liabilities	0.0	0.0
Level 3 | Other liabilities
Defined Contribution Plan Disclosure [Line Items]
Total liabilities	0.0	0.0
Fair Value, Measurements, Recurring | Level 1 | Short-term investments
Defined Contribution Plan Disclosure [Line Items]
Total assets	6.4	1.6
Fair Value, Measurements, Recurring | Level 1 | Other assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	1.6	15.7
Fair Value, Measurements, Recurring | Level 1 | Asset-backed securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	0.0	0.0
Fair Value, Measurements, Recurring | Level 1 | Corporate bonds
Defined Contribution Plan Disclosure [Line Items]
Total assets	0.0	0.0
Fair Value, Measurements, Recurring | Level 1 | Tax-exempt securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	0.0	0.0
Fair Value, Measurements, Recurring | Level 1 | Total assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	8.0	17.3
Fair Value, Measurements, Recurring | Level 2 | Short-term investments
Defined Contribution Plan Disclosure [Line Items]
Total assets	0.0	0.0
Fair Value, Measurements, Recurring | Level 2 | Other assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	0.0	0.0
Fair Value, Measurements, Recurring | Level 2 | Asset-backed securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	0.4	0.5
Fair Value, Measurements, Recurring | Level 2 | Corporate bonds
Defined Contribution Plan Disclosure [Line Items]
Total assets	45.1	47.8
Fair Value, Measurements, Recurring | Level 2 | Tax-exempt securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	32.0	34.9
Fair Value, Measurements, Recurring | Level 2 | Total assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	77.5	83.2
Fair Value, Measurements, Recurring | Level 3 | Short-term investments
Defined Contribution Plan Disclosure [Line Items]
Total assets	0.0	0.0
Fair Value, Measurements, Recurring | Level 3 | Other assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	0.0	0.0
Fair Value, Measurements, Recurring | Level 3 | Asset-backed securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	0.0	0.0
Fair Value, Measurements, Recurring | Level 3 | Corporate bonds
Defined Contribution Plan Disclosure [Line Items]
Total assets	0.0	0.0
Fair Value, Measurements, Recurring | Level 3 | Tax-exempt securities
Defined Contribution Plan Disclosure [Line Items]
Total assets	0.0	0.0
Fair Value, Measurements, Recurring | Level 3 | Total assets
Defined Contribution Plan Disclosure [Line Items]
Total assets	$ 0.0	$ 0.0