Stock Compensation Plans - Performance Share Activity (Detail) - Performance Shares [Member] - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Nonvested Restricted Stock Units Activities [Line Items]
Shares outstanding beginning balance	366
Shares vested	(128)
Shares awarded	85
Shares forfeited	(153)
Shares outstanding ending balance	170	366
Weighted average remaining term (Years) beginning balance	1 year 8 months 16 days	1 year 7 months 21 days
Aggregate intrinsic value, Beginning balance	$ 6,123
Shares vested	1,978
Shares awarded	1,423
Shares forfeited	2,184
Aggregate intrinsic value, Ending balance	$ 2,321	$ 6,123