Stock-Based Compensation - Equity-Classified Stock Compensation (Non-Qualified Stock Option Awards) - Additional Information (Detail) - Non-Qualified Stock Option Award [Member] - USD ($)					9 Months Ended	12 Months Ended
	Jun. 29, 2015	May. 20, 2015	Feb. 09, 2015	Jan. 23, 2013	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiry of option					(a) the tenth anniversary of the grant date; (b) twelve months after the employee’s death or termination for disability; or (c) thirty days after the termination of employment for any reason other than death or disability.
Stock based compensation, Shares, Granted					70,000
Weighted-average grant-date fair value of options granted					$ 14.12
Total intrinsic value of options exercised					$ 408,000
Unrecognized compensation cost related to market condition non-vested restricted shares					$ 822,000
Weighted average period of compensation cost to be recognized					1 year 9 months 18 days
Mr Albright [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiry of option					(a) January 28, 2025; (b) twelve months after the employee’s death or termination for disability; or (c) thirty days after the termination of employment for any reason other than death or disability.
Percent of options vested in each anniversaries, description					The option vests on January 28, 2016, provided he is an employee of the Company on that date.
Mr Patten [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiry of option					(a) the fifth anniversary of the grant date; (b) twelve months after the employee’s death or termination for disability; or (c) thirty days after the termination of employment for any reason other than death or disability.
Percent of options vested in each anniversaries, description					One-third of these options will vest on each of the first, second, and third anniversaries of the grant date, provided the recipient is an employee of the Company on those dates.
Certain Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiry of option					(a) June 29, 2025; (b) twelve months after the employee’s death or termination for disability; or (c) thirty days after the termination of employment for any reason other than death or disability.
Percent of options vested in each anniversaries, description					One-third of the option will vest on each of the first, second, and third anniversaries of the grant date, provided the recipient is an employee of the Company on such dates.
2010 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, Shares, Granted	10,000			51,000
Options granted exercise price	$ 57.54
2010 Plan [Member] | Mr Albright [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, Shares, Granted								50,000
Stock based compensation, Shares, Granted		40,000	20,000
Options granted exercise price		$ 55.62	$ 57.50
2010 Plan [Member] | Mr Patten [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, Shares, Granted							10,000
Stock based compensation, Shares, Granted				10,000
2010 Plan [Member] | Mr Smith [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, Shares, Granted						10,000