Fair Value Measurements: - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Events triggering election	No
Interest Rate Swap \| Other Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Decrease in fair value of interest rate swaps to reflect non-performance risk		$ 2.9
Reported Value Measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Included in current portion of debt - Level 2	$ 6,099.3	$ 5,785.7

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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- Definition

This item represents information describing the nature of certain events which have occurred and thereby allow the fair value option to be elected for a previously ineligible item. Such events may consist of: (1) (a) an investment becoming subject to the equity method of accounting (for example, an investment may previously had been reported as a security categorized as trading or available-for-sale and the level of investment has increased sufficiently to mandate the equity method of accounting) or (b) a subsidiary or variable interest entity ceases to be consolidated but a continuing interest is retained (for example, a majority voting interest is no longer held but the Company continues to hold some common stock); or (2) an event that requires an eligible item to be measured at fair value at the time of the event but does not require fair value measurement at each reporting date after that, excluding the recognition of impairment under lower-of-cost-or-market accounting or other-than-temporary impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14217-108612

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- Definition

Amount of unrealized gain (loss) related to the fair value of interest rate derivatives designated as fair value hedging instruments, as offset by the gain (loss) on the hedged item to the extent that the fair value hedge is determined to be effective.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

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