Stock-Based Compensation Plans (Employee stock purchase plan) - Additional Information (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Maximum number of shares issuable under the ESPP	250		250
Percentage of share purchase price			85.00%
Discount on the share purchases			15.00%
Employee stock purchase plan description, compensation expense	$ 55	$ 103	$ 164	$ 181