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Stock-Based Compensation - Performance Stock Units (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
PSUs
Units
Non-vested at beginning of period (in shares)	1,200,541
Granted (in shares)	928,215
Forfeited (in shares)	(5,142)
Vested (in shares)	(1,330,053)
Non-vested at end of period (in shares)	793,561	1,200,541
Weighted Average Grant-Date Fair Value per Unit
Non-vested at beginning of period (in usd per share)	$ 26.65
Granted (in usd per share)	23.75	$ 22.50	$ 35.36
Forfeited (in usd per share)	35.77
Vested (in usd per share)	15.91
Non-vested at end of period (in usd per share)	41.69	$ 26.65
RPSUs
Weighted Average Grant-Date Fair Value per Unit
Granted (in usd per share)	$ 45.60
Award vesting, percentage	200.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility	30.15%	40.72%	47.52%	43.96%
Expected term (in years)	3 years	3 years	3 years	3 years
Risk free rate	1.58%	2.45%	2.01%	1.50%
RPSUs | 2017
Weighted Average Grant-Date Fair Value per Unit
Granted (in usd per share)	$ 15.91
MSUs
Units
Non-vested at end of period (in shares)	4,260
Weighted Average Grant-Date Fair Value per Unit
Granted (in usd per share)	$ 15.28
Award vesting, percentage	200.00%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility					34.33%
Expected term (in years)					3 years
Risk free rate					1.31%

X

- Definition

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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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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Percentage of vesting of award under share-based payment arrangement.

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Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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