Income Taxes (Recognized Income Tax Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Federal:
Current	$ 4,827	$ (4,638)	$ 2,507
Deferred	28,637	24,121	46,089
Total federal income tax	33,464	19,483	48,596
State:
Current	2,061	1,888	(897)
Deferred	(744)	1,941	1,816
Total state income tax	1,317	3,829	919
Generation (amortization) of accumulated investment tax credits	(750)	3,056	1,489
Total income tax expense	$ 34,031	$ 26,368	$ 51,004