Restructuring Charges - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Mar. 31, 2013	Sep. 30, 2013
Restructuring Cost and Reserve [Line Items]
Percentage of staff reduced by the Corporation		3.40%
Restructuring charges	$ (5)	$ 539	$ 534
Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges		437	437
Fixed Asset Retirement [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 102