Fair Value Measurements - Assets and Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Assets:
Gross derivative assets	$ 423.2	$ 378.5
Liabilities:
Gross derivative liabilities	400.6	349.5
Fair value measured on recurring basis
Assets:
Total assets at fair value	435.7	389.9
Liabilities:
Total liabilities at fair value	400.6	349.5
Fair value measured on recurring basis | Level 1 Inputs
Assets:
Total assets at fair value	290.1	233.5
Liabilities:
Total liabilities at fair value	277.3	223.0
Fair value measured on recurring basis | Level 2 Inputs
Assets and liabilities measured at estimated fair value on a recurring basis
Debt	523.5	524.7
Notes receivable	44.3	45.7
Assets:
Total assets at fair value	140.6	146.8
Liabilities:
Total liabilities at fair value	118.3	120.2
Fair value measured on recurring basis | Level 3 Inputs
Assets:
Total assets at fair value	5.0	9.5
Liabilities:
Total liabilities at fair value	5.0	6.3
Commodity contracts | Fair value measured on recurring basis
Assets:
Gross derivative assets	410.9	371.0
Liabilities:
Gross derivative liabilities	391.9	326.0
Commodity contracts | Fair value measured on recurring basis | Level 1 Inputs
Assets:
Gross derivative assets	290.1	233.5
Liabilities:
Gross derivative liabilities	277.3	223.0
Commodity contracts | Fair value measured on recurring basis | Level 2 Inputs
Assets:
Gross derivative assets	115.8	127.9
Liabilities:
Gross derivative liabilities	109.6	96.8
Commodity contracts | Fair value measured on recurring basis | Level 3 Inputs
Assets:
Gross derivative assets	5.0	9.5
Liabilities:
Gross derivative liabilities	5.0	6.3
Foreign currency contracts | Fair value measured on recurring basis
Assets:
Gross derivative assets	9.5	7.5
Liabilities:
Gross derivative liabilities	7.4	19.8
Foreign currency contracts | Fair value measured on recurring basis | Level 1 Inputs
Assets:
Gross derivative assets	0.0	0.0
Liabilities:
Gross derivative liabilities	0.0	0.0
Foreign currency contracts | Fair value measured on recurring basis | Level 2 Inputs
Assets:
Gross derivative assets	9.5	7.5
Liabilities:
Gross derivative liabilities	7.4	19.8
Foreign currency contracts | Fair value measured on recurring basis | Level 3 Inputs
Assets:
Gross derivative assets	0.0	0.0
Liabilities:
Gross derivative liabilities	0.0	0.0
Interest rate contracts | Fair value measured on recurring basis
Assets:
Gross derivative assets	2.8
Liabilities:
Gross derivative liabilities	1.3	3.7
Interest rate contracts | Fair value measured on recurring basis | Level 1 Inputs
Assets:
Gross derivative assets	0.0
Liabilities:
Gross derivative liabilities	0.0	0.0
Interest rate contracts | Fair value measured on recurring basis | Level 2 Inputs
Assets:
Gross derivative assets	2.8
Liabilities:
Gross derivative liabilities	1.3	3.7
Interest rate contracts | Fair value measured on recurring basis | Level 3 Inputs
Assets:
Gross derivative assets	0.0
Liabilities:
Gross derivative liabilities	0.0	0.0
Cash surrender value of life insurance | Fair value measured on recurring basis
Assets:
Cash surrender value of life insurance	12.5	11.4
Cash surrender value of life insurance | Fair value measured on recurring basis | Level 1 Inputs
Assets:
Cash surrender value of life insurance	0.0	0.0
Cash surrender value of life insurance | Fair value measured on recurring basis | Level 2 Inputs
Assets:
Cash surrender value of life insurance	12.5	11.4
Cash surrender value of life insurance | Fair value measured on recurring basis | Level 3 Inputs
Assets:
Cash surrender value of life insurance	$ 0.0	$ 0.0