Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value, Measurement Inputs, Disclosure [Table Text Block]

Assets and liabilities measured at fair value on a recurring basis as of December 31, 2018 and 2017 is summarized in the following tables.



Dollar amounts in millions	December 31, 2018		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Available for sale securities	$	6.1	$	—	$	—	$	6.1
Trading securities	3.1		3.1		—		—



Dollar amounts in millions	December 31, 2017		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Available for sale securities	$	6.0	$	—	$	—	$	6.0
Trading securities	3.1		3.1		—		—

Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

The following table summarizes changes in assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) during the twelve months ended December 31, 2018 and 2017.



Dollar amounts in millions	Available for sale securities
Balance at December 31, 2016	$	4.8
Total realized/unrealized gains
Included in other comprehensive income	1.2
Balance at December 31, 2017	$	6.0
Return of principal on ARS	0.4
Total realized/unrealized gains
Included in investment income	(0.4		)
Included in other comprehensive income	0.1
Balance at December 31, 2018	$	6.1