Fair Value Measurements (Long-term Fixed Interest Rate Debt) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Senior Notes | 5.250% Senior notes due 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate (percent)	5.25%
Senior Notes | 4.625% Senior notes due 2027
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate (percent)	4.625%
Carrying value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	$ 1,179.0	$ 1,166.6
Carrying value | Senior Notes | 5.250% Senior notes due 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	300.0	300.0
Carrying value | Senior Notes | 4.625% Senior notes due 2027
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	400.0	400.0
Carrying value | Real estate mortgages and other debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	479.0	466.6
Fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	1,143.9	1,195.7
Fair value | Senior Notes | 5.250% Senior notes due 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	270.0	315.0
Fair value | Senior Notes | 4.625% Senior notes due 2027
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	346.5	412.0
Fair value | Real estate mortgages and other debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	$ 527.4	$ 468.7