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Pension Benefits (Details) - USD ($) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Jan. 01, 2018 | Jan. 01, 2017
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |  |  |  |  |
Projected benefit obligation at beginning of year |  | $ 66,086,000 | $ 71,937,000 |  |  |  |
Defined Benefit Plan, service cost |  | 5,582,000 | 6,730,000 | $ 6,638,000 |  |  |
Defined Benefit Plan, interest cost |  | 2,791,000 | 2,622,000 | 2,689,000 |  |  |
Defined Benefit Plan, actuarial (gain) loss |  | 2,035,000 | (7,155,000) |  |  |  |
Defined Benefit Plan, benefits paid |  | (5,651,000) | (8,048,000) |  |  |  |
Projected benefit obligation at end of year |  | 70,843,000 | 66,086,000 | 71,937,000 |  |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |  |  |  |  |
Defined Benefit Plan, fair value of plan assets at beginning of year |  | 30,100,000 | 30,978,000 |  |  |  |
Defined Benefit Plan, actual return on plan assets |  | 3,985,000 | (964,000) |  |  |  |
Defined Benefit Plan, employer contribution |  | 7,200,000 | 8,134,000 | 7,000,000.0 |  |  |
Defined Benefit Plan, benefits paid |  | (5,651,000) | (8,048,000) | (10,800,000) |  |  |
Defined Benefit Plan, fair value of plan assets at end of year |  | 35,634,000 | 30,100,000 | 30,978,000 |  |  |
Defined Benefit Plan, funded status at end of year |  | (35,209,000) | (35,986,000) |  |  |  |
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract] |  |  |  |  |  |  |
Defined Benefit Plan, projected benefit obligation |  | 70,843,000 | 66,086,000 |  |  |  |
Defined Benefit Plan, accumulated benefit obligation |  | 60,877,000 | 52,368,000 |  |  |  |
Defined Benefit Plan, fair value of plan assets |  | 35,634,000 | 30,100,000 |  |  |  |
Defined Benefit Plan, underfunded accumulated benefit obligation |  | $ 25,243,000 | 22,268,000 |  |  |  |
Defined Benefit Plan, unrecognized net gain (loss) amortization threshold |  | 10.00% |  |  |  |  |
Pre-tax Amounts Recognized in Accumulated Other Comprehensive Income [Abstract] |  |  |  |  |  |  |
Defined Benefit Plan, unrecognized actuarial losses |  | $ 14,406,000 | 15,741,000 |  |  |  |
Defined Benefit Plan, unrecognized prior service costs |  | 31,000 | 48,000 |  |  |  |
Defined Benefit Plan, accumulated other comprehensive loss |  | 14,437,000 | 15,789,000 |  |  |  |
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract] |  |  |  |  |  |  |
Other Comprehensive Income (Loss), Defined Benefit Plan, net actuarial gain (loss) |  | 377,000 | 4,329,000 | (2,995,000) |  |  |
Other Comprehensive Income (Loss), Defined Benefit Plan, amortization of prior service cost |  | 17,000 | 18,000 | 17,000 |  |  |
Other Comprehensive Income (Loss), Defined Benefit Plan, amortization of net actuarial loss |  | 958,000 | 1,327,000 | 1,297,000 |  |  |
Other Comprehensive Income (Loss), Defined Benefit Plan, settlements |  | 0 | 0 | 3,009,000 |  |  |
Other Comprehensive Income (Loss), Defined Benefit Plan, total pension liability adjustment, pre-tax |  | 1,352,000 | 5,674,000 | 1,328,000 |  |  |
Other Comprehensive Income (Loss), Defined Benefit Plan, tax (expense) benefit |  | (291,000) | (4,265,000) | (561,000) |  |  |
Other Comprehensive Income (Loss), Defined Benefit Plan, cumulative effect of accounting change | [1] |  |  |  | $ 0 |  | $ 44,732,000
Other Comprehensive Income (Loss), Defined Benefit Plan, total pension liability adjustment, net | [2] | (1,061,000) | (4,378,000) | (767,000) |  |  |
Components of Net Periodic Benefit Costs for Both Pension Plans |  |  |  |  |  |  |
Defined Benefit Plan, service cost |  | 5,582,000 | 6,730,000 | 6,638,000 |  |  |
Defined Benefit Plan, interest cost |  | 2,791,000 | 2,622,000 | 2,689,000 |  |  |
Defined Benefit Plan, expected return on plan assets that reduces periodic pension benefit cost |  | (1,574,000) | (1,862,000) | (2,244,000) |  |  |
Defined Benefit Plan, amortization of prior service cost |  | 17,000 | 18,000 | 17,000 |  |  |
Defined Benefit Plan, amortization of net actuarial loss |  | 958,000 | 1,327,000 | 1,297,000 |  |  |
Defined Benefit Plan, settlements |  | 0 | 0 | 3,009,000 |  |  |
Defined Benefit Plan, net periodic benefit cost |  | $ 7,774,000 | $ 8,835,000 | $ 11,406,000 |  |  |
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation and Net Periodic Benefit Cost [Abstract] |  |  |  |  |  |  |
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, discount rate |  | 3.60% | 4.40% |  |  |  |
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, rate of compensation increase |  | 4.50% | 6.20% |  |  |  |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, discount rate |  | 4.40% | 3.80% | 4.20% |  |  |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, expected return on plan assets | [3] | 5.00% | 5.50% | 6.50% |  |  |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, rate of compensation increase |  | 6.20% | 6.20% | 6.20% |  |  |
Defined Benefit Plan, Expected Future Employer Contributions [Abstract] |  |  |  |  |  |  |
Defined Benefit Plan, Expected Future Contributions in Next Fiscal Year |  | $ 5,600,000 |  |  |  |  |
Future Benefit Payments |  |  |  |  |  |  |
Defined Benefit Plan, Expected Future Benefit Payments in Year One |  | 7,609,000 |  |  |  |  |
Defined Benefit Plan, Expected Future Benefit Payments in Year Two |  | 3,914,000 |  |  |  |  |
Defined Benefit Plan, Expected Future Benefit Payments in Year Three |  | 4,022,000 |  |  |  |  |
Defined Benefit Plan, Expected Future Benefit Payments in Year Four |  | 6,308,000 |  |  |  |  |
Defined Benefit Plan, Expected Future Benefit Payments in Year Five |  | 4,939,000 |  |  |  |  |
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter |  | 25,065,000 |  |  |  |  |
Nonqualified Plan [Member] |  |  |  |  |  |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |  |  |  |  |
Defined Benefit Plan, fair value of plan assets at beginning of year |  | 0 | $ 0 |  |  |  |
Defined Benefit Plan, fair value of plan assets at end of year |  | $ 0 | $ 0 | $ 0 |  |  |
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation and Net Periodic Benefit Cost [Abstract] |  |  |  |  |  |  |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, expected return on plan assets |  | 0.00% | 0.00% | 0.00% |  |  |
Equity Securities [Member] |  |  |  |  |  |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |  |  |  |  |
Defined Benefit Plan, fair value of plan assets at beginning of year |  | $ 9,580,000 |  |  |  |  |
Defined Benefit Plan, fair value of plan assets at end of year |  | 13,134,000 | $ 9,580,000 |  |  |  |
Fixed Income Securities [Member] |  |  |  |  |  |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |  |  |  |  |
Defined Benefit Plan, fair value of plan assets at beginning of year |  | 12,420,000 |  |  |  |  |
Defined Benefit Plan, fair value of plan assets at end of year |  | 13,578,000 | 12,420,000 |  |  |  |
Other Securities [Member] |  |  |  |  |  |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |  |  |  |  |  |
Defined Benefit Plan, fair value of plan assets at beginning of year |  | 8,100,000 |  |  |  |  |
Defined Benefit Plan, fair value of plan assets at end of year |  | 8,922,000 | $ 8,100,000 |  |  |  |
Accounting Standards Update 2018-02 [Member] |  |  |  |  |  |  |
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) [Abstract] |  |  |  |  |  |  |
Other Comprehensive Income (Loss), Defined Benefit Plan, cumulative effect of accounting change |  | $ 0 |  | $ 0 | $ 2,969,000 | [4] |
[1] | (1) Please refer to Recently Issued Accounting Standards in Note 1 – Summary of Significant Accounting Policies for additional information.
[2] | (1) Please refer to Note 8 – Pension Benefits for additional discussion on the pension liability adjustment.
[3] | (1) There is no assumed expected return on plan assets for the Nonqualified Pension Plan because there are no plan assets in the Nonqualified Pension Plan.
[4] | (1) Please refer to Recently Issued Accounting Standards in Note 1 – Summary of Significant Accounting Policies and Statements of Stockholders’ Equity for additional information.

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- Definition Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669686-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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- Definition Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(6) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964 + Details
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