Stock-based compensation (Tables)

12 Months Ended

Dec. 29, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]

The following table summarizes stock option activity for the year endedDecember 29, 2018:

				Weighted-
				average
		Weighted-		remaining
		average		contractual	Aggregate
	Stock options	exercise price		term (years)	intrinsic value
Outstanding, beginning of year	3,306,728	$	7.51
Granted	58,000		7.56
Exercised	(222,880)		4.11
Forfeited	(443,298)		7.76
Outstanding, end of year	2,698,550	$	7.76	6.67	$	210
Exercisable, end of year	1,264,902	$	7.18	5.04	$	127

The following table summarizes non-vested stock option activity during the year ended December 29, 2018:

		Weighted-
		average grant-
	Stock options	date fair value
Non-vested, beginning of year	2,149,221	$	3.57
Granted	58,000		3.31
Vested	(524,657)		3.19
Forfeited	(248,916)		3.22
Non-vested, end of year	1,433,648	$	3.74

Schedule of Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding [Table Text Block]

The following table summarizes non-vested stock option activity during the year ended December 29, 2018:

					Weighted-
					average
					remaining	Weighted-			Weighted-
Exercise price range				Outstanding	contractual life	average exercise		Exercisable	average exercise
	Low		High	options	(years)	price		options	price
$	3.27	$	5.50	468,550	6.85	$	3.68	297,447	$	3.75
	5.51		7.28	527,377	5.76		6.24	302,043		5.91
	7.29		9.35	578,999	6.48		8.03	333,502		7.67
	9.36		9.60	687,445	8.40		9.50	1,667		9.45
	9.61		13.86	436,179	5.14		10.85	330,243		10.92
				2,698,550	6.67	$	7.76	1,264,902	$	7.18

Schedule Of Share Based Compensation - RSU [Table Text Block]

The following table summarizes non-vested RSU activity during the year ended December 29, 2018:

		Weighted-
		average grant-
	RSUs	date fair value
Non-vested, beginning of year	775,356	$	8.85
Granted	154,711		7.65
Vested	(314,326)		8.96
Forfeited	(17,904)		9.50
Non-vested, end of year	597,837	$	8.46

Schedule Of Share Based Compensation - PSU [Table Text Block]

The following table summarizes non-vested PSU activity during the year ended December 29, 2018:

		Weighted-
		average grant-
	PSUs	date fair value
Non-vested, beginning of year	1,519,752	$	5.68
Forfeited or cancelled	(157,856)		6.41
Non-vested, end of year	1,361,896	$	5.60

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

The weighted-average grant-date fair values of all stock options granted in the years ended December 29, 2018, December 30, 2017 and December 31, 2016, were $3.31, $4.12 and $1.86, respectively. The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the stock options granted in those years were as follows:

	December 29, 2018		December 30, 2017		December 31, 2016
Grant-date stock price	$	7.56	$	9.29	$	4.25
Dividend yield(1)		0%		0%		0%
Expected volatility(2)		41.1%		42.1%		41.7%
Risk-free interest rate(3)		2.9%		2.0%		1.6%
Expected life of options (years)(4)		6.0		6.4		6.0

(1)Determined based on expected annual dividend yield at the time of grant.

(2)Determined based on historical volatility of the Company’s Common Shares over the expected life of the option.

(3)Determined based on the yield on U.S. Treasury zero-coupon issues with maturity dates equal to the expected life of the option.

(4)Determined using simplified method, as the Company changed the vesting period of its stock option grants from five years to three years in 2016, and, as a result, historical exercise data may not provide a reasonable basis upon which to estimate expected life.

The grant-date weighted-average fair value of the PSUs was determined to be $5.64, based on the following inputs to the valuation model:

	December 30, 2017
Grant-date stock price	$	9.33
Dividend yield		0%
Expected volatility(1)		42.2%
Risk-free interest rate(2)		1.5%
Expected life (in years)(3)		3.0

(1) Determined based on the historical volatility of the Common Shares over 6.5 years, which is consistent with the volatility assumption for stock options granted to employees.

(2) Determined based on U.S. Treasury yields with a remaining term equal to the expected life of the PSUs.

(3) Determined based on vesting for the PSUs.

Schedule Of Share Based Payment Award Employee Stock Purchase Plan Valuation Assumptions Table [Text Block]

For the year endedDecember 29, 2018, the grant-date weighted-average fair values of the Special Stock Options and PSUs were estimated using a Monte Carlo valuation model and determined to be $1.84 and $2.79, respectively, based on the following inputs to the valuation model:

	December 30, 2017
		Special Stock
		Options		PSUs
Grant-date stock price	$	7.00	$	7.00
Exercise price	$	7.00		NA
Dividend yield		0%		0%
Expected volatility(1)		42.0%		42.0%
Risk-free interest rate(2)		2.2%		1.5%
Expected life (in years)(3)		6.5		3.0

(1)Determined based on the historical volatility of the Common Shares over the expected life of the Special Stock Options.

(2) Determined based on U.S. Treasury yields with a remaining term equal to the respective expected lives of the Special Stock Options and PSUs.

(3) Determined using the simplified method for the Special Stock Options, based on the mid-point of vesting (three years) and expiration (ten years). Determined based on vesting for the PSUs.