Investments (Tables)

12 Months Ended

Dec. 31, 2015

Investments [Abstract]

Unrealized Gain (Loss) on Investments [Table Text Block]

The following table summarizes unrealized gains and losses related to these investments as of December 31, 2015 and December 31, 2014:

Dollar amounts in millions	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
December 31, 2015
Auction rate securities	$	0.4	$	5.4	$	—	$	5.8
Total marketable securities	$	0.4	$	5.4	$	—	$	5.8
December 31, 2014
Auction rate securities	$	0.3	$	4.3	$	—	$	4.6
Total marketable securities	$	0.3	$	4.3	$	—	$	4.6

Investments Classified by Contractual Maturity Date [Table Text Block]

The contractual maturities of debt securities classified as available for sale at December 31, 2015 were as follows:

Dollar amounts in millions	2015
	Amortized Cost		Fair Value
Due in one year or less	$	—	$	—
Due in more than one year	0.4		5.8
Total marketable securities	$	0.4	$	5.8