Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Comprehensive income:
Net income	$ 240.9	$ 239.9
Defined benefit pension plan:
Actuarial (loss) gain arising during period, net of tax	(0.9)	0.2
Actuarial gain and prior service cost included in net periodic pension cost, net of tax	(2.3)	0.1
Total defined benefit pension plan, net of tax	(3.2)	0.3
Unrealized gain (loss) on available-for-sale securities, net of tax	19.9	(31.6)
Other comprehensive income (loss), net of tax	16.7	(31.3)
Comprehensive income	$ 257.6	$ 208.6