Debt (Tables)

6 Months Ended

Jun. 30, 2016

Debt Disclosure [Abstract]

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

The amortized cost of debt outstanding at June 30, 2016 and December 31, 2015 was:

(Dollars in Millions)	Jun 30, 2016		Dec 31, 2015
Senior Notes:
6.00% Senior Notes due May 15, 2017	$	359.4	$	359.1
4.35% Senior Notes due February 15, 2025	247.6		247.4
7.375% Subordinated Debentures due February 27, 2054	144.1		144.1
Total Debt Outstanding	$	751.1	$	750.6

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, 2016 and 2015 was:

	Six Months Ended						Three Months Ended
(Dollars in Millions)	Jun 30, 2016			Jun 30, 2015			Jun 30, 2016			Jun 30, 2015
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			—			—
6.00% Senior Notes due May 15, 2017	11.1			11.1			5.5			5.5
4.35% Senior Notes due February 15, 2025	5.6			3.9			2.8			2.8
7.375% Subordinated Debentures due February 27, 2054	5.5			5.5			2.7			2.7
Interest Expense before Capitalization of Interest	22.6			24.6			11.2			11.2
Capitalization of Interest	(0.3		)	(0.5		)	(0.1		)	(0.3		)
Total Interest Expense	$	22.3		$	24.1		$	11.1		$	10.9

Schedule of Interest Paid [Table Text Block]

Interest paid, including facility fees, for the six and three months endedJune 30, 2016 and 2015 was:

	Six Months Ended				Three Months Ended
(Dollars in Millions)	Jun 30, 2016		Jun 30, 2015		Jun 30, 2016		Jun 30, 2015
Notes Payable under Revolving Credit Agreement	$	0.3	$	1.1	$	0.2	$	0.9
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		—		—
6.00% Senior Notes due May 15, 2017	10.8		10.8		10.8		10.8
4.35% Senior Notes due February 15, 2025	5.4		—		—		—
7.375% Subordinated Debentures due February 27, 2054	5.5		5.5		2.7		2.7
Total Interest Paid	$	22.0	$	22.2	$	13.7	$	14.4