Stock-Based Compensation - Equity-Classified Stock Compensation (Market Condition Grants of Restricted Shares) - Additional Information (Detail)	3 Months Ended			9 Months Ended	12 Months Ended
	Jun. 30, 2015 $ / shares shares	Mar. 31, 2015 shares	Dec. 31, 2014 shares	Sep. 30, 2015 USD ($) Increment $ / shares shares	Dec. 31, 2012 shares	Dec. 31, 2011 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares vesting description				The restricted shares will vest in six increments based upon the price per share of the Company’s common stock during the term of their employment (or within sixty days after termination of employment by the Company without cause), meeting or exceeding the target trailing sixty-day average closing prices ranging from $36 per share for the first increment to $65 per share for the final increment.
Restricted share award closing prices range per share, Minimum				$ 36
Restricted share award closing prices range per share, Maximum				$ 65
Restricted share award average closing prices, period				60 days
Number of increments had vested | Increment				6
Mr Albright [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares vesting description				The restricted stock will vest in seven increments based upon the price per share of Company common stock during the term of his employment (or within sixty days after termination of employment by the Company without cause), meeting or exceeding the target trailing thirty-day average closing prices ranging from $60 per share for the first increment to $90 per share for the final increment.
Restricted share award closing prices range per share, Minimum	$ 60
Restricted share award closing prices range per share, Maximum	$ 90
Restricted share award average closing prices, period	30 days
Number of increments had vested | Increment				4
Mr Patten [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of increments had vested | Increment				4
Mr Smith [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares vesting description				The restricted stock will vest in two increments based upon the price per share of Company common stock during the term of their employment (or within sixty days after termination of employment by the Company without cause), meeting or exceeding the target trailing sixty-day average closing prices of $60 per share and $65 per share for the two increments.
Restricted share award closing prices range per share, Minimum				$ 60
Restricted share award closing prices range per share, Maximum				$ 65
Restricted share award average closing prices, period				60 days
Number of increments had vested | Increment				0
Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of increments had vested | Increment				0
Restricted Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to market condition non-vested restricted shares | $				$ 4,000
Weighted average period of compensation cost to be recognized				2 months 12 days
Restricted Shares [Member] | 2010 Plan [Member] | Mr Albright [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, Shares, Granted | shares	94,000				96,000	96,000
Restricted Shares [Member] | 2010 Plan [Member] | Mr Patten [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, Shares, Granted | shares					17,000	17,000
Restricted Shares [Member] | 2010 Plan [Member] | Mr Smith [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, Shares, Granted | shares			2,500
Restricted Shares [Member] | 2010 Plan [Member] | Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, Shares, Granted | shares		3,000
Inducement Grant of Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, Shares, Granted | shares				97,000
Unrecognized compensation cost related to market condition non-vested restricted shares | $				$ 2,700,000
Weighted average period of compensation cost to be recognized				1 year 4 months 24 days