Allowance and Other Reserves - Balances and Activity of Allowance and Reserve (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	$ 1.6
Balance at end of year	3.9	$ 1.6
Reserve for cash basis tenants
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	0.9	0.0
Additions	10.6	0.0
Deductions or other	1.2	0.9
Balance at end of year	12.7	0.9	$ 0.0
Allowance for doubtful accounts
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	0.6	2.0	1.4
Additions	3.6	(0.4)	1.3
Deductions or other	(1.3)	(1.0)	(0.7)
Balance at end of year	2.6	0.6	2.0
Allowance for doubtful accounts \| Impact of adoption of new accounting standards
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	(0.3)
Balance at end of year		(0.3)
Reserve for contract credits
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	2.3	0.0
Additions	0.0	2.3
Deductions or other	0.0	0.0
Balance at end of year	2.3	2.3	0.0
Allowance for credit losses - financing receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	0.0
Additions	(0.4)
Deductions or other	0.0
Balance at end of year	3.9	0.0
Allowance for credit losses - financing receivables \| Impact of adoption of new accounting standards
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	1.6
Balance at end of year		1.6
Allowance for credit losses - financing receivables \| Impact of adoption of new accounting standards \| (Distribution in Excess of Accumulated Earnings) Earnings Surplus
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	2.7
Balance at end of year		2.7
Allowance for credit losses - contract assets
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	0.0
Additions	(0.9)
Deductions or other	(0.1)
Balance at end of year	0.7	0.0
Allowance for credit losses - contract assets \| Impact of adoption of new accounting standards
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	0.3
Balance at end of year		0.3
Allowance for credit losses - contract assets \| Impact of adoption of new accounting standards \| (Distribution in Excess of Accumulated Earnings) Earnings Surplus
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	1.4
Balance at end of year		1.4
Loans allowance
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	1.6	1.6	1.6
Additions	0.0	0.0	0.0
Deductions or other	0.0	0.0	0.0
Balance at end of year	0.0	1.6	1.6
Loans allowance \| Impact of adoption of new accounting standards
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	(1.6)
Balance at end of year		(1.6)
Other reserves
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	0.4	0.4	0.4
Additions	0.0	0.0	0.0
Deductions or other	(0.4)	0.0	0.0
Balance at end of year	$ 0.0	$ 0.4	$ 0.4

Financing Receivable, Allowance for Credit Loss [Roll Forward]