Income Tax (Tables)

3 Months Ended

Mar. 31, 2016

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

	Three Months Ended March 31,
Dollars in thousands	2016			2015
Income taxes at statutory rates (federal and state)	$	24,608		$	18,892
Increase (decrease):
Differences required to be flowed-through by regulatory commissions	1,518			1,329
Other, net	(740		)	(1,138		)
Total provision for income taxes	$	25,386		$	19,083
Effective tax rate	40.9		%	40.1		%