Compensation Expense Associated with Stock-Settled Performance Units (Detail) - Performance Units Awards - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense associated with Stock-Settled Performance Units	$ 1,013
2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense associated with Stock-Settled Performance Units	1,796	$ 1,347
2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense associated with Stock-Settled Performance Units	1,855	1,855	$ 1,391
2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense associated with Stock-Settled Performance Units	$ 255	1,022	1,022
2011
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense associated with Stock-Settled Performance Units		$ 464	1,856
2010
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense associated with Stock-Settled Performance Units			$ 260