Basis of Presentation and Significant Accounting Policies Supplemental Cash Flow Information (Tables)

12 Months Ended

Dec. 31, 2017

Schedule of Cash Flow Supplemental Information [Line Items]

Schedule of Supplemental Cash Flow Information [Table Text Block]

Supplemental Disclosure of Cash Flow Information:

(Dollars in thousands) Year Ended December 31,	2017		2016		2015
Cash paid during the period for:
Income taxes	$	40,334	$	21,437	$	16,969
Interest on long-term debt and investment agreements	39,112		4,537		1,847
Non-cash financing activities:
Decrease in long-term debt as a result of an exchange for investment securities	55,426		—		—