Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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- Definition

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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-Publisher FASB
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- Definition

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).

+ References

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- Definition

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.

+ References

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-Paragraph 2
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- Definition

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

+ References

No definition available.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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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.

+ References

No definition available.

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- Definition

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

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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Share-Based Compensation - Nonvested Restricted Stock Units (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted Shares
Non-vested, beginning balance (in shares)	3,978,433
Granted (in shares)	899,269	946,570	943,160
Vested (in shares)	(866,259)
Forfeited (in shares)	(50,883)
Non-vested, ending balance (in shares)	3,960,560	3,978,433
Weighted- Average Grant- Date Fair Value
Non-vested, beginning balance (usd per share)	$ 24.90
Granted (usd per share	28.30	$ 27.20	$ 26.56
Vested (usd per share)	25.24
Forfeited (usd per share)	25.54
Non-vested, ending balance (usd per share)	$ 25.59	$ 24.90
Class B common stock bonus
Restricted Shares
Granted (in shares)	451,769
Weighted- Average Grant- Date Fair Value
Vesting period, years	3 years
Class B common stock key employees
Restricted Shares
Granted (in shares)	447,500
Weighted- Average Grant- Date Fair Value
Vesting period, years	10 years