Shareholders' Equity Stock Awards (Details) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 30, 2017 USD ($) $ / shares shares
Restricted Stock [Member]
Stock awards [Roll Forward]
Outstanding at December 31, 2016 \| shares	530,000
Granted \| shares	217,000
Vested \| shares	(312,000)
Canceled/Forfeited \| shares	(40,000)
Outstanding at December 30, 2017 \| shares	395,000
Weighted-Average Grant Date Fair Value
Outstanding at December 31, 2016 \| $ / shares	$ 20.83
Granted \| $ / shares	25.81
Vested \| $ / shares	20.35
Canceled/Forfeited \| $ / shares	22.47
Outstanding at December 30, 2017 \| $ / shares	$ 23.77
Stock-based compensation expense related to non-vested awards \| $	$ 5.5
Weighted average period to recognize remaining expense over	1 year 9 months 18 days
Performance-Based and Market-Based Stock Award [Member]
Stock awards [Roll Forward]
Outstanding at December 31, 2016 \| shares	899,000
Granted \| shares	568,000
Vested \| shares	(338,000)
Canceled/Forfeited \| shares	(66,000)
Outstanding at December 30, 2017 \| shares	1,063,000
Weighted-Average Grant Date Fair Value
Outstanding at December 31, 2016 \| $ / shares	$ 20.87
Granted \| $ / shares	23.03
Vested \| $ / shares	16.73
Canceled/Forfeited \| $ / shares	19.88
Outstanding at December 30, 2017 \| $ / shares	$ 23.41
Stock-based compensation expense related to non-vested awards \| $	$ 15.2
Weighted average period to recognize remaining expense over	2 years 1 month 6 days
Performance-Based Stock Award with a Market Condition [Member]
Stock awards [Roll Forward]
Granted \| shares	270,895
Weighted-Average Grant Date Fair Value
Granted \| $ / shares	$ 22.40
Fair value assumptions, method used	Monte Carlo simulation model
Expected dividend yield (in hundredths)	0.00%
Expected volatility (in hundredths)	46.00%
Risk-free interest rate (in hundredths)	1.50%

Time-based awards and performance stock awards [Roll Forward]

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- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, 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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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- Definition

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).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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- Definition

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.

+ References

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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-Paragraph 2
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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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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
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- Definition

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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- Definition

For each plan, identification of the award pricing model or other valuation method used in calculating the weighted average fair values disclosed. The model is also used to calculate the compensation expense that is shown within the balance sheet, income statement, and cash flow. Examples of valuation techniques are lattice models (binomial model), closed-form models (Black-Scholes-Merton formula), and a Monte Carlo simulation technique. Fair value is the amount at which an asset or liability could be bought or incurred or sold or settled in a current transaction between willing parties, that is, other than in a forced or liquidation sale. May include disclosures about the assumptions underlying application of the method selected.

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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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