Changes in Deferred Stock Units Related to Quarterly Grants (Detail) (Deferred Stock Units, USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Deferred Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of DSUs, Granted and vested	3,815	8,378	13,483	23,750
Expense Recognized, Granted and vested	$ 82	$ 97	$ 240	$ 288