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Share and Unit-based Plans - Stock Units Roll Forward Activity (Details) - Stock units	12 Months Ended
	Dec. 31, 2020 $ / shares shares	Dec. 31, 2019 $ / shares shares	Dec. 31, 2018 $ / shares shares
Share-based Payment Arrangement [Abstract]
Number of common shares into which units can be converted (in shares)	1
Shares or Units
Balance at beginning of year (in shares) | shares	199,987	129,457	151,355
Granted (in shares) | shares	253,184	160,932	87,983
Vested (in shares) | shares	(140,224)	(85,157)	(108,991)
Forfeited (in shares) | shares	(3,102)	(5,245)	(890)
Balance at end of year (in shares) | shares	309,845	199,987	129,457
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Balance at beginning of year (in dollars per share) | $ / shares	$ 43.59	$ 64.21	$ 73.32
Granted (in dollars per share) | $ / shares	14.14	37.44	58.79
Vested (in dollars per share) | $ / shares	39.53	62.84	74.04
Forfeited (in dollars per share) | $ / shares	32.62	51.48	68.81
Balance at end of year (in dollars per share) | $ / shares	$ 21.47	$ 43.59	$ 64.21

X

- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments, Other than Options, Conversion Rate

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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