Supplemental Cash Flow Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Open reverse repurchase commitments	$ 0	$ 0	$ 0
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	22,500,000	55,900,000
Income Taxes Paid	363,200,000	574,100,000
Interest Paid, Excluding Capitalized Interest, Operating Activities	102,600,000	112,000,000.0
Operating Lease, Payments	41,800,000	44,800,000
Cash and Cash Equivalents
Open reverse repurchase commitments	140,600,000	90,500,000	$ 137,100,000
Common equities | Quarterly dividend
Dividends Payable	$ 58,500,000	$ 58,500,000