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		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Deferred Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of DSUs, Granted and vested	3,755	7,888	9,668	15,372
Expense Recognized, Granted and vested	$ 80	$ 96	$ 159	$ 191