Stock-based compensation plans (Details) | 1 Months Ended | 3 Months Ended | 6 Months Ended | 9 Months Ended | 12 Months Ended |
Dec. 31, 2015USD ($)Employee$ / sharesshares | Jul. 02, 2016USD ($)$ / sharesshares | Jul. 04, 2015USD ($) | Apr. 04, 2015USD ($)Employee$ / sharesshares | Jul. 02, 2016USD ($)Employee$ / sharesshares | Jul. 04, 2015USD ($)$ / sharesshares | Sep. 30, 2015USD ($)$ / sharesshares |
Weighted Average Grant-Date Fair Value [Abstract] | | | | | | | |
Stock based compensation expense | $ | | $ 169,000 | $ 147,000 | | $ 527,000 | $ 406,000 | |
Unrecognized compensation expense | $ | | $ 679,000 | | | $ 679,000 | | |
Weighted average period for unrecognized compensation expense to be recognized | | | | | 1 year 10 months 24 days | | |
Stock Options [Member] | | | | | | | |
Fair Value of Stock Options using Black-Scholes-Merton Option-Pricing Model [Abstract] | | | | | | | |
Expected life | | | | | 4 years | | |
Risk-free interest rate | | | | | 1.55% | | |
Volatility | | | | | 61.43% | | |
Dividend yield | | | | | 0.00% | | |
Weighted-average fair value per share (in dollars per share) | $ / shares | | | | | $ 4.81 | | |
Outstanding Shares [Abstract] | | | | | | | |
Outstanding shares, beginning balance (in shares) | | | | | 0 | | |
Outstanding shares, granted (in shares) | | | | | 38,460 | | |
Outstanding shares, exercised (in shares) | | | | | 0 | | |
Outstanding shares, forfeited or expired (in shares) | | | | | 0 | | |
Outstanding shares, ending balance (in shares) | | 38,460 | | | 38,460 | | 0 |
Outstanding shares, exercisable (in shares) | | 0 | | | 0 | | |
Outstanding shares, vested and expected to vest (in shares) | | 34,737 | | | 34,737 | | |
Weighted Average Exercise Price [Abstract] | | | | | | | |
Weighted average exercise price, beginning balance (in dollars per share) | $ / shares | | | | | $ 0 | | |
Weighted average exercise price, granted (in dollars per share) | $ / shares | | | | | 9.94 | | |
Weighted average exercise price, exercised (in dollars per share) | $ / shares | | | | | 0 | | |
Weighted average exercise price, forfeited or expired (in dollars per share) | $ / shares | | | | | 0 | | |
Weighted average exercise price, ending balance (in dollars per share) | $ / shares | | $ 9.94 | | | 9.94 | | $ 0 |
Weighted average exercise price, exercisable (in dollars per share) | $ / shares | | 0 | | | 0 | | |
Weighted average exercise price, vested and expected to vest (in dollars per share) | $ / shares | | $ 9.94 | | | $ 9.94 | | |
Weighted Average Remaining Contractual Term [Abstract] | | | | | | | |
Weighted average remaining contractual term | | | | | 4 years 5 months 16 days | | 0 years |
Weighted average remaining contractual term, granted | | | | | 5 years | | |
Weighted average remaining contractual term, exercised | | | | | 0 years | | |
Weighted average remaining contractual term, forfeited or expired | | | | | 0 years | | |
Weighted average remaining contractual term, exercisable | | | | | 0 years | | |
Weighted average remaining contractual term, vested and expected to vest | | | | | 4 years 5 months 16 days | | |
Aggregate Intrinsic Value [Abstract] | | | | | | | |
Aggregate intrinsic value, beginning balance | $ | | | | | $ 0 | | |
Aggregate intrinsic value, granted | $ | | | | | 11,153 | | |
Aggregate intrinsic value, exercised | $ | | | | | 0 | | |
Aggregate intrinsic value, forfeited or expired | $ | | | | | 0 | | |
Aggregate intrinsic value, ending balance | $ | | | | | | | $ 0 |
Aggregate intrinsic value, exercisable | $ | | 0 | | | 0 | | |
Aggregate intrinsic value, vested and expected to vest | $ | | | | | | | |
Number of shares of Stock Options [Abstract] | | | | | | | |
Non-vested balance, beginning of period (in shares) | | | | | 0 | | |
Granted (in shares) | | | | | 38,460 | | |
Vested (in shares) | | | | | 0 | | |
Non-vested balance, end of period (in shares) | | 38,460 | | | 38,460 | | 0 |
Weighted Average Grant-Date Fair Value [Abstract] | | | | | | | |
Non-vested balance, beginning of period (in dollars per share) | $ / shares | | | | | $ 0 | | |
Granted (in dollars per share) | $ / shares | | | | | 4.81 | | |
Vested (in dollars per share) | $ / shares | | | | | 0 | | |
Non-vested balance, ending of period (in dollars per share) | $ / shares | | $ 4.81 | | | $ 4.81 | | $ 0 |
Restricted Stock [Member] | | | | | | | |
Number of shares of Restricted Stock [Roll Forward] | | | | | | | |
Non-vested balance, beginning of period (in shares) | | | | 168,600 | 196,600 | 168,600 | 168,600 |
Granted (in shares) | | | | | 41,240 | | 92,600 |
Cancelled (in shares) | | | | | (3,300) | | |
Vested (in shares) | | | | | (91,600) | | (64,600) |
Non-vested balance, end of period (in shares) | | 142,940 | | | 142,940 | | 196,600 |
Weighted Average Grant-Date Fair Value [Roll Forward] | | | | | | | |
Non-vested balance, beginning of period (in dollars per share) | $ / shares | | | | $ 5.27 | $ 5.97 | $ 5.27 | $ 5.27 |
Granted (in dollars per share) | $ / shares | | | | | 9.89 | | 7.49 |
Cancelled (in dollars per share) | $ / shares | | | | | 9.82 | | |
Vested (in dollars per share) | $ / shares | | | | | 6.72 | | 6.32 |
Non-vested balance, ending of period (in dollars per share) | $ / shares | | $ 6.53 | | | $ 6.53 | | $ 5.97 |
Weighted Average Grant-Date Fair Value [Abstract] | | | | | | | |
Charge to income for restricted stock | $ | | | | $ 65,000 | | | |
Restricted Stock [Member] | Nine Non-Employees [Member] | | | | | | | |
Number of shares of Restricted Stock [Roll Forward] | | | | | | | |
Granted (in shares) | | | | 30,600 | 29,700 | | |
Weighted Average Grant-Date Fair Value [Abstract] | | | | | | | |
Number of employees directors with restricted stock grant | Employee | | | | 9 | 9 | | |
Estimated fair value of stock at date of grant | $ | | | | $ 225,000 | $ 292,000 | | |
Period for recognition of unearned compensation | | | | 12 months | 12 months | | |
Charge to income for restricted stock | $ | | | | $ 131,000 | $ 94,000 | | |
Quarterly charge to income for restricted stock | $ | | | | | 65,000 | | |
Restricted Stock [Member] | Four Employees [Member] | | | | | | | |
Number of shares of Restricted Stock [Roll Forward] | | | | | | | |
Granted (in shares) | 11,540 | | | | | | |
Weighted Average Grant-Date Fair Value [Abstract] | | | | | | | |
Number of employees directors with restricted stock grant | Employee | 4 | | | | | | |
Estimated fair value of stock at date of grant | $ | $ 116,000 | | | | | | |
Period for recognition of unearned compensation | 3 years | | | | | | |
Charge to income for restricted stock | $ | | $ 8,000 | | | $ 18,000 | | |
Quarterly charge to income for restricted stock | $ | $ 8,000 | | | | | | |
Performance Shares [Member] | Nine Non-Employees [Member] | | | | | | | |
Weighted Average Grant-Date Fair Value [Abstract] | | | | | | | |
Number of employees directors with restricted stock grant | Employee | 9 | | | | | | |
Exercise price (in dollars per share) | $ / shares | $ 9.94 | | | | | | |
Estimated fair value of stock at date of grant | $ | $ 185,000 | | | | | | |
Period for recognition of unearned compensation | 3 years | | | | | | |
Quarterly charge to income for restricted stock | $ | $ 14,000 | | | | | | |
1996 Equity Incentive Plan [Member] | | | | | | | |
Weighted Average Grant-Date Fair Value [Abstract] | | | | | | | |
Shares reserved and available for grant (in shares) | | 336,990 | | | 336,990 | | 139,578 |