Restructuring Accrual - Narrative (Details) $ in Millions	3 Months Ended					6 Months Ended	9 Months Ended
	Mar. 31, 2021 USD ($) employee	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) employee	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($) employee
Restructuring Cost and Reserve [Line Items]
Amount accrued in the period	$ 1.4			$ 2.3			$ 14.3	$ 16.0
Acquisition, disposition, and restructuring related activities	(85.8)			6.5			(67.5)	20.1
Gain (loss) from discontinued operations, net of income taxes	0.0			5.0			0.0	(25.3)
Restructuring liability, current portion	7.6						7.6
Unallocated Corporate
Restructuring Cost and Reserve [Line Items]
Amount accrued in the period	0.0			0.6			0.6	3.1
2020 Performance Improvement Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring charges						$ 12.9
Acquisition, disposition, and restructuring related activities								15.3
Gain (loss) from discontinued operations, net of income taxes								$ 3.7
2020 Performance Improvement Restructuring Plan | Unallocated Corporate
Restructuring Cost and Reserve [Line Items]
Number of employees affected | employee								10
National Media | Operating Segments
Restructuring Cost and Reserve [Line Items]
Amount accrued in the period	1.3			1.7			6.4	$ 10.5
National Media | 2020 Performance Improvement Restructuring Plan | Operating Segments
Restructuring Cost and Reserve [Line Items]
Number of employees affected | employee								145
Local Media | Operating Segments
Restructuring Cost and Reserve [Line Items]
Amount accrued in the period	0.1			0.0			$ 7.3	$ 2.4
Local Media | 2020 Performance Improvement Restructuring Plan | Operating Segments
Restructuring Cost and Reserve [Line Items]
Number of employees affected | employee								15
Employee Severance | 2021 Performance Improvement Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 1.4	$ 0.5	$ 12.4
Employee Severance | 2021 Performance Improvement Restructuring Plan | Unallocated Corporate
Restructuring Cost and Reserve [Line Items]
Number of employees affected | employee			10
Employee Severance | 2020 Performance Improvement Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring charges				$ 2.3	$ 3.8	9.9
Employee Severance | National Media | 2021 Performance Improvement Restructuring Plan | Operating Segments
Restructuring Cost and Reserve [Line Items]
Number of employees affected | employee			80
Employee Severance | Local Media | 2021 Performance Improvement Restructuring Plan | Operating Segments
Restructuring Cost and Reserve [Line Items]
Number of employees affected | employee	25		140
Other Restructuring | 2020 Performance Improvement Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring charges						$ 3.0