Retirement and Postretirement Plans - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2030
Long Term Growth Plan One [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets		$ 1,274.0
Long Term Growth Plan Two [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets		288.1
Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit credit	$ 35.4
Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension benefit obligations funded by plan assets		1,738.0
Defined benefit plan, plan assets		$ 1,562.5	$ 2,152.4	$ 2,221.8
Percentage of benefit obligations included in funded by plan assets		90.00%
Defined benefit plan obligation underfunded amount		$ 216.8	104.7
Benefit obligations of retirement plans		1,779.3	2,257.1	2,553.5
Defined benefit plan obligation underfunded amount		175.4
Defined benefit retirement plans recognized gain related to settlement			12.5	1.6
Defined benefit plan benefit obligation increased		415.9	84.9
Increase (decrease) in projected benefit obligation for pension plans		2.4	4.4
Defined benefit plan benefit obligation period increase (decrease) due to decrease in discount rates		26.1	8.7
Net periodic benefit credit		$ 42.5	80.7	45.8
Postretirement Health Care [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care costs annual rate of increase (decrease) in the per capita cost		6.25%
Postretirement Health Care [Member] | Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care costs annual rate of increase (decrease) in the per capita cost					(4.50%)
Health care obligations annual rate of increase (decrease) in the per capita cost					4.50%
Retirement savings plans Nexstar [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan obligation underfunded amount		$ 21.3	27.2
Benefit obligations of retirement plans		21.3	27.2	29.6
Net periodic benefit credit		(0.7)	(1.1)	(0.8)
Contributions by employer		14.3	$ 16.2	$ 14.9
Supplemental Executive Retirement and ERISA Excess Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligations of retirement plans		$ 41.4
Maximum [Member] | Long Term Growth Plan One [Member] | U.S. Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		28.00%
Maximum [Member] | Long Term Growth Plan One [Member] | Non-U.S. Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		16.00%
Maximum [Member] | Long Term Growth Plan One [Member] | Emerging Market Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		13.00%
Maximum [Member] | Long Term Growth Plan One [Member] | Global Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		17.00%
Maximum [Member] | Long Term Growth Plan One [Member] | Opportunistic Sub-asset Classes [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		17.00%
Maximum [Member] | Long Term Growth Plan One [Member] | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		0.00%
Maximum [Member] | Long Term Growth Plan One [Member] | Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		5.00%
Maximum [Member] | Long Term Growth Plan Two [Member] | U.S. Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		18.00%
Maximum [Member] | Long Term Growth Plan Two [Member] | Non-U.S. Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		12.00%
Maximum [Member] | Long Term Growth Plan Two [Member] | Emerging Market Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		11.00%
Maximum [Member] | Long Term Growth Plan Two [Member] | Global Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		15.00%
Maximum [Member] | Long Term Growth Plan Two [Member] | Opportunistic Sub-asset Classes [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		14.00%
Maximum [Member] | Long Term Growth Plan Two [Member] | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		0.00%
Maximum [Member] | Long Term Growth Plan Two [Member] | Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		10.00%
Maximum [Member] | Scenario, Forecast [Member] | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range	80.00%
Maximum [Member] | Postretirement Health Care [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care obligations annual rate of increase (decrease) in the per capita cost		8.50%
Minimum [Member] | Long Term Growth Plan One [Member] | U.S. Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		8.00%
Minimum [Member] | Long Term Growth Plan One [Member] | Non-U.S. Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		0.00%
Minimum [Member] | Long Term Growth Plan One [Member] | Emerging Market Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		0.00%
Minimum [Member] | Long Term Growth Plan One [Member] | Global Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		0.00%
Minimum [Member] | Long Term Growth Plan One [Member] | Opportunistic Sub-asset Classes [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		0.00%
Minimum [Member] | Long Term Growth Plan One [Member] | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		0.00%
Minimum [Member] | Long Term Growth Plan One [Member] | Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		0.00%
Minimum [Member] | Long Term Growth Plan Two [Member] | U.S. Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		0.00%
Minimum [Member] | Long Term Growth Plan Two [Member] | Non-U.S. Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		0.00%
Minimum [Member] | Long Term Growth Plan Two [Member] | Emerging Market Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		0.00%
Minimum [Member] | Long Term Growth Plan Two [Member] | Global Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		0.00%
Minimum [Member] | Long Term Growth Plan Two [Member] | Opportunistic Sub-asset Classes [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		0.00%
Minimum [Member] | Long Term Growth Plan Two [Member] | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		0.00%
Minimum [Member] | Long Term Growth Plan Two [Member] | Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range		0.00%
Minimum [Member] | Scenario, Forecast [Member] | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range	60.00%
Minimum [Member] | Postretirement Health Care [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care obligations annual rate of increase (decrease) in the per capita cost		6.00%