Retirement and Compensation Plans Funding Status and Net Periodic Pension Costs (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets beginning of period	$ 315,457,000
Fair Value of Plan Assets, End of period	361,336,000	$ 315,457,000
Pension Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation	319,931,000	375,999,000
Defined Benefit Plan, Service Cost	4,549,000	5,973,000	$ 5,552,000
Defined Benefit Plan, Interest Cost	13,273,000	13,642,000	14,124,000
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(51,338,000)	20,594,000
Defined Benefit Plan, Benefit Obligation, Benefits Paid	7,971,000	4,001,000
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	0	56,256,000
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits	0	5,168,000
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation	381,120,000	319,931,000	375,999,000
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets beginning of period	316,008,000	345,396,000
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	39,827,000	869,000
Defined Benefit Plan, Plan Assets, Contributions by Employer	15,000,000	30,000,000
Defined Benefit Plan, Plan Assets, Benefits Paid	7,971,000	4,001,000
Defined Benefit Plan, Plan Assets, Payment for Settlement	0	56,256,000
Fair Value of Plan Assets, End of period	362,864,000	316,008,000	345,396,000
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(18,256,000)	(3,923,000)
Defined Benefit Plan, Accumulated Benefit Obligation	343,029,000	287,052,000
Other Pension Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation	25,363,000	26,914,000
Defined Benefit Plan, Service Cost	467,000	539,000	436,000
Defined Benefit Plan, Interest Cost	992,000	958,000	1,003,000
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(2,930,000)	1,170,000
Defined Benefit Plan, Benefit Obligation, Benefits Paid	1,829,000	1,878,000
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	0	0
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation	27,923,000	25,363,000	26,914,000
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets beginning of period	0	0
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	0	0
Defined Benefit Plan, Plan Assets, Contributions by Employer	1,829,000	1,878,000
Defined Benefit Plan, Plan Assets, Benefits Paid	1,829,000	1,878,000
Defined Benefit Plan, Plan Assets, Payment for Settlement	0	0
Fair Value of Plan Assets, End of period	0	0	$ 0
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(27,923,000)	(25,363,000)
Defined Benefit Plan, Accumulated Benefit Obligation	$ 25,471,000	$ 22,753,000