Debt (Tables)

6 Months Ended

Jun. 30, 2015

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments [Table Text Block]

The amortized cost of debt outstanding at June 30, 2015 and December 31, 2014 was:

(Dollars in Millions)	Jun 30, 2015		Dec 31, 2014
Senior Notes:
6.00% Senior Notes due November 30, 2015	$	—	$	249.5
6.00% Senior Notes due May 15, 2017	358.8		358.5
4.35% Senior Notes due February 15, 2025	247.3		—
7.375% Subordinated Debentures due February 27, 2054	144.1		144.1
Total Debt Outstanding	$	750.2	$	752.1

Schedule of Interest Expense [Table Text Block]

Interest Expense, including facility fees, accretion of discount and amortization of issuance costs, for the six and three months endedJune 30, 2015 and 2014 was:

	Six Months Ended						Three Months Ended
(Dollars in Millions)	Jun 30, 2015			Jun 30, 2014			Jun 30, 2015			Jun 30, 2014
Notes Payable under Revolving Credit Agreement	$	0.4		$	0.4		$	0.2		$	0.2
Federal Home Loan Bank of Dallas	—			—			—			—
Federal Home Loan Bank of Chicago	—			—			—			—
Senior Notes Payable:
6.00% Senior Notes due November 30, 2015	3.7			7.7			—			3.8
6.00% Senior Notes due May 15, 2017	11.1			11.1			5.5			5.6
4.35% Senior Notes due February 15, 2025	3.9			—			2.8			—
7.375% Subordinated Debentures due February 27, 2054	5.5			3.8			2.7			2.8
Interest Expense before Capitalization of Interest	24.6			23.0			11.2			12.4
Capitalization of Interest	(0.5		)	(0.5		)	(0.3		)	(0.2		)
Total Interest Expense	$	24.1		$	22.5		$	10.9		$	12.2

Schedule of Interest Paid [Table Text Block]

Interest paid, including facility fees, for the six and three months endedJune 30, 2015 and 2014 was:

	Six Months Ended				Three Months Ended
(Dollars in Millions)	Jun 30, 2015		Jun 30, 2014		Jun 30, 2015		Jun 30, 2014
Notes Payable under Revolving Credit Agreement	$	1.1	$	0.3	$	0.9	$	0.1
Federal Home Loan Bank of Dallas	—		—		—		—
Federal Home Loan Bank of Chicago	—		—		—		—
Senior Notes Payable:
6.00% Senior Notes due November 30, 2015	4.8		7.5		—		7.5
6.00% Senior Notes due May 15, 2017	10.8		10.8		10.8		10.8
4.35% Senior Notes due February 15, 2025	—		—		—		—
7.375% Subordinated Debentures due February 27, 2054	5.5		2.8		2.7		2.8
Total Interest Paid	$	22.2	$	21.4	$	14.4	$	21.2