Benefit Plans Plan Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 260,747	$ 133,459
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,801	8,136
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	243,521	127,610	$ 133,360
Pension Plan [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 86,288	$ 42,654
Actual plan asset allocations as a percent of toal plan assets	36.00%	33.00%
Pension Plan [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 146,210	$ 77,053
Actual plan asset allocations as a percent of toal plan assets	60.00%	60.00%
Pension Plan [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 11,023	$ 7,903
Actual plan asset allocations as a percent of toal plan assets	5.00%	6.00%
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 17,226	$ 5,849	$ 6,804
Other Postretirement Benefits Plan [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 5,608	$ 2,200
Actual plan asset allocations as a percent of toal plan assets	33.00%	38.00%
Other Postretirement Benefits Plan [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 10,840	$ 3,416
Actual plan asset allocations as a percent of toal plan assets	63.00%	58.00%
Other Postretirement Benefits Plan [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 778	$ 233
Actual plan asset allocations as a percent of toal plan assets	5.00%	4.00%