Income Taxes - Summary of Tax Credit Carryforwards (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Income Taxes Disclosure [Line Items]
Net operating loss carryover	$ 463.8	$ 511.2
Tax credit carryover	86.6	55.1
Capital loss carryover	8.6	$ 9.0
Net operating loss carryover valuation allowance	401.6
Tax credit carryover valuation allowance	46.7
Capital loss carryover valuation allowance	8.6
1-5 Years [Member]
Income Taxes Disclosure [Line Items]
Net operating loss carryover	3.3
Tax credit carryover	15.1
Capital loss carryover	1.7
6-10 Years [Member]
Income Taxes Disclosure [Line Items]
Net operating loss carryover	52.7
Tax credit carryover	62.4
11+ Years [Member]
Income Taxes Disclosure [Line Items]
Net operating loss carryover	279.5
Tax credit carryover	1.6
Indefinite [Member]
Income Taxes Disclosure [Line Items]
Net operating loss carryover	128.3
Tax credit carryover	7.5
Capital loss carryover	$ 6.9