Business Combinations (Details) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Goodwill	$ 714,963,000	$ 681,358,000	$ 664,922,000
Asset Retirement Obligation	446,919,000	$ 417,575,000	$ 375,553,000
2020 Acquisition [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Gross Aggregate Consideration	110,200,000
Cash Assumed	1,700,000
Business Combination, Consideration Transferred	106,000,000.0
Business Combination, Indemnity Holdback Liability	2,500,000
Business Combination, Current Assets	54,800,000
Business Combination, Property, Plant, and Equipment	27,100,000
Goodwill	33,600,000
Business Combination, Other Intangible Assets	19,000,000.0
Business Combination, Current Liabilities	22,600,000
Business Combination, Noncurrent Liabilities	300,000
Asset Retirement Obligation	$ 1,400,000

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Amount of liability recognized arising from contingent consideration in a business combination.

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Amount of currency on hand as well as demand deposits with banks or financial institutions, acquired at the acquisition date. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of assets that are expected to be realized or consumed within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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The amount of identifiable intangible assets recognized as of the acquisition date.

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Amount of liabilities due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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The amount of property, plant, and equipment recognized as of the acquisition date.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

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