Income Taxes - Income Taxes (Narrative) (Details) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) restaurant	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) restaurant	Dec. 31, 2017 USD ($)
Income Tax Examination [Line Items]
Goodwill, impairment loss	$ 92.2	$ 92.2
Non-deductibility of goodwill impairment		17.90%	0.00%	0.00%
Changes in tax rates and state tax laws		0.40%	0.50%	1.60%
Proceeds from income tax refunds		$ 12.3
Interest income		1.1
Deferred tax assets, foreign tax credit carryforward		3.0
Operating loss carryforwards		13.3	$ 0.5
Unrecognized tax benefits		2.2	7.6	$ 5.2	$ 5.9
Unrecognized tax benefit changes in next 12 months		0.8
Unrecognized tax benefits, interest on income taxes accrued		0.9	2.5
Unrecognized tax benefits, income tax penalties accrued		$ 0.1	$ 0.1
Applebee's
Income Tax Examination [Line Items]
Number of restaurants | restaurant		1,711
Applebee's | Entity Operated Units
Income Tax Examination [Line Items]
Goodwill, impairment loss		$ 0.0
Number of restaurants | restaurant		69		69