Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
State tax net operating loss carryforwards, net of federal tax effect	$ 71.8	$ 79.4
Allowance for loan losses and non-accrual interest	65.5	62.3
Acquisition-related deferred tax assets	30.5	13.3
Tax credits and net operating loss carryforwards	24.7	0.0
Equity-based compensation	18.1	15.6
ROU lease assets, net of lease liabilities	7.5
D.C. Solar investment basis difference	6.8	0.0
Unrealized loss on debt securities transferred to held-to-maturity	3.6	4.7
Unrealized loss on debt securities available-for-sale	0.0	15.4
Other deductible temporary differences	28.2	28.5
Total deferred tax assets	256.7	219.2
Less: valuation allowance for state deferred tax assets	(72.4)	(80.1)
Total deferred tax assets, net of the valuation allowance	184.3	139.1
Deferred tax liabilities:
Leasing activities	(92.7)	(82.0)
Pension and other postretirement benefits	(20.0)	(9.7)
Book over tax income recognized on consumer loans	(18.0)	(17.5)
Unrealized gain on debt securities available-for-sale	(6.6)	0.0
Mark-to-market and original issue discounts for tax purposes	(5.2)	(10.4)
Temporary differences related to merchant services joint venture	(3.5)	(3.7)
Other taxable temporary differences	(4.7)	(4.4)
Total deferred tax liabilities	(150.7)	(127.7)
Net deferred tax asset	$ 33.6	$ 11.4