Income Taxes (Tax Carryforwards) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Deferred Tax Asset Balance	$ 186,402	$ 189,445
Valuation Allowance	0	(3,431)
Total deferred tax assets	186,402	$ 186,014
State | Net Operating Loss | 2023-2027
Operating Loss Carryforwards [Line Items]
Deferred Tax Asset Balance	1,431
Valuation Allowance	0
Total deferred tax assets	1,431
Pre-Tax Earnings Necessary to Realize	1,429,499
State | Net Operating Loss | 2028-2032
Operating Loss Carryforwards [Line Items]
Deferred Tax Asset Balance	39,483
Valuation Allowance	0
Total deferred tax assets	39,483
Pre-Tax Earnings Necessary to Realize	914,384
State | Net Operating Loss | 2033-2036
Operating Loss Carryforwards [Line Items]
Deferred Tax Asset Balance	356
Valuation Allowance	0
Total deferred tax assets	356
Pre-Tax Earnings Necessary to Realize	7,356
State | Other Credits | 2019-2023
Operating Loss Carryforwards [Line Items]
Deferred Tax Asset Balance	20,164
Valuation Allowance	0
Total deferred tax assets	20,164
State | Other Credits | 2024-2028
Operating Loss Carryforwards [Line Items]
Deferred Tax Asset Balance	2,388
Valuation Allowance	0
Total deferred tax assets	$ 2,388