Fair Value Measurements - Assets and Liabilities (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Assets and liabilities measured at estimated fair value on a recurring basis
Debt	$ 910,200,000	$ 1,186,300,000
Total derivative assets	312,000,000.0	347,200,000
Gross Amounts Recognized	332,500,000	332,500,000
Transfers from Level 1 to Level 2, assets	0	0
Transfers from Level 2 to Level 1, assets	0	0
Transfers from Level 1 to Level 2, liabilities	0	0
Transfers from Level 2 to Level 1, liabilities	0	0
Commodity contracts
Assets and liabilities measured at estimated fair value on a recurring basis
Total derivative assets	303,600,000	331,200,000
Gross Amounts Recognized	323,900,000	326,100,000
Foreign currency contracts
Assets and liabilities measured at estimated fair value on a recurring basis
Total derivative assets	8,500,000	16,000,000.0
Gross Amounts Recognized	8,700,000	6,400,000
Fair value measured on recurring basis
Assets and liabilities measured at estimated fair value on a recurring basis
Total assets	317,700,000	351,200,000
Total liabilities	332,500,000	332,500,000
Fair value measured on recurring basis | Cash surrender value of life insurance
Assets and liabilities measured at estimated fair value on a recurring basis
Cash surrender value of life insurance	5,600,000	4,000,000.0
Fair value measured on recurring basis | Commodity contracts
Assets and liabilities measured at estimated fair value on a recurring basis
Total derivative assets	303,600,000	331,200,000
Gross Amounts Recognized	323,900,000	326,100,000
Fair value measured on recurring basis | Foreign currency contracts
Assets and liabilities measured at estimated fair value on a recurring basis
Total derivative assets	8,500,000	16,000,000.0
Gross Amounts Recognized	8,700,000	6,400,000
Level 1 | Fair value measured on recurring basis
Assets and liabilities measured at estimated fair value on a recurring basis
Total assets	196,300,000	273,600,000
Total liabilities	210,600,000	236,600,000
Level 1 | Fair value measured on recurring basis | Cash surrender value of life insurance
Assets and liabilities measured at estimated fair value on a recurring basis
Cash surrender value of life insurance	0	0
Level 1 | Fair value measured on recurring basis | Commodity contracts
Assets and liabilities measured at estimated fair value on a recurring basis
Total derivative assets	196,300,000	273,600,000
Gross Amounts Recognized	210,600,000	236,600,000
Level 1 | Fair value measured on recurring basis | Foreign currency contracts
Assets and liabilities measured at estimated fair value on a recurring basis
Total derivative assets	0	0
Gross Amounts Recognized	0	0
Level 2 | Cash surrender value of life insurance
Assets and liabilities measured at estimated fair value on a recurring basis
Cash surrender value of life insurance	5,600,000
Level 2 | Fair value measured on recurring basis
Assets and liabilities measured at estimated fair value on a recurring basis
Debt	900,000,000	1,200,000,000
Notes receivable	44,900,000	16,900,000
Total assets	120,200,000	75,300,000
Total liabilities	120,500,000	95,200,000
Level 2 | Fair value measured on recurring basis | Cash surrender value of life insurance
Assets and liabilities measured at estimated fair value on a recurring basis
Cash surrender value of life insurance		4,000,000.0
Level 2 | Fair value measured on recurring basis | Commodity contracts
Assets and liabilities measured at estimated fair value on a recurring basis
Total derivative assets	106,100,000	55,300,000
Gross Amounts Recognized	111,800,000	88,800,000
Level 2 | Fair value measured on recurring basis | Foreign currency contracts
Assets and liabilities measured at estimated fair value on a recurring basis
Total derivative assets	8,500,000	16,000,000.0
Gross Amounts Recognized	8,700,000	6,400,000
Level 3 | Fair value measured on recurring basis
Assets and liabilities measured at estimated fair value on a recurring basis
Total assets	1,200,000	2,300,000
Total liabilities	1,400,000	700,000
Level 3 | Fair value measured on recurring basis | Cash surrender value of life insurance
Assets and liabilities measured at estimated fair value on a recurring basis
Cash surrender value of life insurance	0	0
Level 3 | Fair value measured on recurring basis | Commodity contracts
Assets and liabilities measured at estimated fair value on a recurring basis
Total derivative assets	1,200,000	2,300,000
Gross Amounts Recognized	1,400,000	700,000
Level 3 | Fair value measured on recurring basis | Foreign currency contracts
Assets and liabilities measured at estimated fair value on a recurring basis
Total derivative assets	0	0
Gross Amounts Recognized	$ 0	$ 0