Recent Authoritative Accounting Guidance (Details) - USD ($) $ in Millions	Jun. 30, 2020	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total stockholders’ equity	$ 1,998.9	$ 1,956.1		$ 2,013.9	$ 1,948.6	$ 1,736.9	$ 1,693.9
Off-Balance Sheet, Credit Loss, Liability				0.0
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Off-Balance Sheet, Credit Loss, Liability			$ 2.3
Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses			30.0
Deferred tax assets			8.2
Retained earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total stockholders’ equity	$ 912.5	$ 897.6		$ 953.6	$ 892.5	$ 874.7	$ 851.8
Retained earnings | Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total stockholders’ equity			24.1
Off-Balance Sheet, Credit Loss, Liability			$ 2.3