Fair Value Measurements (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Carrying amount and estimated fair value of long term debt
Long-term Debt, Carrying Amount	$ 2,827.8	$ 1,792.1
Long-term Debt, Fair Value	2,885.7	1,725.7
Secured Debt Term A [Member]
Carrying amount and estimated fair value of long term debt
Long-term Debt, Carrying Amount	438.5	204.7
Long-term Debt, Fair Value	440.1	197.8
Senior Unsecured Notes Due 2021 [Member] [Domain]
Carrying amount and estimated fair value of long term debt
Long-term Debt, Carrying Amount	299.1	298.5
Long-term Debt, Fair Value	298.4	292.9
Senior Unsecured Notes Due 2023 [Member] [Domain]
Carrying amount and estimated fair value of long term debt
Long-term Debt, Carrying Amount	298.3	297.9
Long-term Debt, Fair Value	307.2	297.5
Senior Unsecured Notes Due 2026 [Member]
Carrying amount and estimated fair value of long term debt
Long-term Debt, Carrying Amount	297.8	297.5
Long-term Debt, Fair Value	305.6	274.5
Senior Unsecured Notes Due 2028 [Member]
Carrying amount and estimated fair value of long term debt
Long-term Debt, Carrying Amount	694.1	693.5
Long-term Debt, Fair Value	734.4	663.0
2018 Revolver [Member]
Carrying amount and estimated fair value of long term debt
Long-term Debt, Carrying Amount	800.0	0.0
Long-term Debt, Fair Value	$ 800.0	$ 0.0