Stock-based compensation plans (Details) | 1 Months Ended | 3 Months Ended | 12 Months Ended |
Dec. 31, 2015USD ($)Employee$ / sharesshares | Dec. 31, 2014USD ($)Employeeshares | Jan. 02, 2016USD ($)Employee$ / sharesshares | Jan. 03, 2015USD ($)$ / sharesshares | Sep. 30, 2015USD ($)$ / sharesshares |
Fair Value of Stock Options using Black-Scholes-Merton Option-Pricing Model [Abstract] | | | | | |
Expected life | | | 4 years 7 days | | |
Risk-free interest rate | | | 1.55% | | |
Volatility | | | 61.43% | | |
Dividend yield | | | 0.00% | | |
Weighted-average fair value per share (in dollars per share) | $ / shares | | | $ 4.82 | | |
Outstanding Shares [Abstract] | | | | | |
Outstanding shares, beginning balance (in shares) | shares | | | 0 | | |
Outstanding shares, granted (in shares) | shares | | | 38,460 | | |
Outstanding shares, exercised (in shares) | shares | | | 0 | | |
Outstanding shares, forfeited or expired (in shares) | shares | | | 0 | | |
Outstanding shares, ending balance (in shares) | shares | | | 38,460 | | 0 |
Outstanding shares, exercisable (in shares) | shares | | | 0 | | |
Outstanding shares, vested and expected to vest (in shares) | shares | | | 35,088 | | |
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 | | | 10.06 | | |
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 | | | 10.06 | | $ 0 |
Weighted average exercise price, exercisable (in dollars per share) | $ / shares | | | 0 | | |
Weighted average exercise price, vested and expected to vest (in dollars per share) | $ / shares | | | $ 10.06 | | |
Weighted Average Remaining Contractual Term [Abstract] | | | | | |
Weighted average remaining contractual term | | | 4 years 11 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 11 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 | $ | | | 11,153 | | $ 0 |
Aggregate intrinsic value, exercisable | $ | | | 0 | | |
Aggregate intrinsic value, vested and expected to vest | $ | | | $ 10,176 | | |
Number of shares of Stock Options [Abstract] | | | | | |
Granted (in shares) | shares | | | 38,460 | | |
Weighted Average Grant-Date Fair Value [Abstract] | | | | | |
Stock based compensation expense | $ | | | $ 152,000 | $ 113,000 | |
Unrecognized compensation expense | $ | | | $ 925,000 | | |
Weighted average period for unrecognized compensation expense to be recognized | | | 2 years 3 months 18 days | | |
Stock Options [Member] | | | | | |
Outstanding Shares [Abstract] | | | | | |
Outstanding shares, granted (in shares) | shares | | | 38,460 | | |
Number of shares of Stock Options [Abstract] | | | | | |
Non-vested balance, beginning of period (in shares) | shares | | | 0 | | |
Granted (in shares) | shares | | | 38,460 | | |
Vested (in shares) | shares | | | 0 | | |
Non-vested balance, end of period (in shares) | shares | | | 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 | | | 7.85 | | |
Vested (in dollars per share) | $ / shares | | | 0 | | |
Non-vested balance, ending of period (in dollars per share) | $ / shares | | | $ 7.85 | | $ 0 |
Restricted Stock [Member] | | | | | |
Number of shares of Restricted Stock [Roll Forward] | | | | | |
Non-vested balance, beginning of period (in shares) | shares | | | 196,600 | 196,600 | 196,600 |
Granted (in shares) | shares | | | 11,540 | | 11,540 |
Vested (in shares) | shares | | | (61,000) | | (61,000) |
Non-vested balance, end of period (in shares) | shares | | | 147,140 | | 196,600 |
Weighted Average Grant-Date Fair Value [Roll Forward] | | | | | |
Non-vested balance, beginning of period (in dollars per share) | $ / shares | | | $ 5.97 | $ 5.97 | $ 5.97 |
Granted (in dollars per share) | $ / shares | | | 7.85 | | 7.85 |
Vested (in dollars per share) | $ / shares | | | 6.41 | | 6.41 |
Non-vested balance, ending of period (in dollars per share) | $ / shares | | | $ 5.94 | | $ 5.97 |
Restricted Stock [Member] | Eight Employees [Member] | | | | | |
Number of shares of Restricted Stock [Roll Forward] | | | | | |
Granted (in shares) | shares | | 42,000 | | | |
Weighted Average Grant-Date Fair Value [Abstract] | | | | | |
Number of employees directors with restricted stock grant | Employee | | 8 | | | |
Estimated fair value of stock at date of grant | $ | | $ 330,000 | | | |
Period for recognition of unearned compensation | | 2 years | | | |
Charge to income for restricted stock | $ | | $ 82,000 | | | |
Quarterly charge to income for restricted stock | $ | | $ 41,000 | | | |
Restricted Stock [Member] | Three Employees [Member] | | | | | |
Number of shares of Restricted Stock [Roll Forward] | | | | | |
Granted (in shares) | shares | | 20,000 | | | |
Weighted Average Grant-Date Fair Value [Abstract] | | | | | |
Number of employees directors with restricted stock grant | Employee | | 3 | | | |
Estimated fair value of stock at date of grant | $ | | $ 139,000 | | | |
Period for recognition of unearned compensation | | 5 years | | | |
Charge to income for restricted stock | $ | | $ 14,000 | | | |
Quarterly charge to income for restricted stock | $ | | $ 7,000 | | | |
Restricted Stock [Member] | Nine Non-Employees [Member] | | | | | |
Number of shares of Restricted Stock [Roll Forward] | | | | | |
Granted (in shares) | shares | | | 30,600 | | |
Weighted Average Grant-Date Fair Value [Abstract] | | | | | |
Number of employees directors with restricted stock grant | Employee | | | 9 | | |
Estimated fair value of stock at date of grant | $ | | | $ 225,000 | | |
Period for recognition of unearned compensation | | | 12 months | | |
Charge to income for restricted stock | $ | | | $ 131,000 | | |
Quarterly charge to income for restricted stock | $ | | | $ 56,000 | | |
Restricted Stock [Member] | Four Employees [Member] | | | | | |
Number of shares of Restricted Stock [Roll Forward] | | | | | |
Granted (in shares) | 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 | $ | $ 116,000,000 | | | | |
Period for recognition of unearned compensation | 3 years | | | | |
Quarterly charge to income for restricted stock | $ | $ 10,000 | | | | |
Performance Shares [Member] | Nine Non-Employees [Member] | | | | | |
Weighted Average Grant-Date Fair Value [Abstract] | | | | | |
Number of employees directors with restricted stock grant | Employee | 9 | | | | |
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 | $ | $ 15,000 | | | | |
Exercise price (Per share) | $ / shares | $ 9.944 | | | | |
1996 Equity Incentive Plan [Member] | | | | | |
Weighted Average Grant-Date Fair Value [Abstract] | | | | | |
Shares reserved and available for grant (in shares) | shares | | | 89,578 | 157,557 | |