Summary of Vesting Information for RSU Awards Granted (Detail) - Restricted Stock Units - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of units vested under compound annualized TSR during performance period	354,058	260,000	0
10% to Less Than 15%
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of units vested under compound annualized TSR during performance period		150,000
15% to Less Than 40%
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of units vested under compound annualized TSR during performance period		250,000
40% or More
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of units vested under compound annualized TSR during performance period		260,000
More Than 8 Percentage Points Below the Russell 2000 Index TSR
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of TSR target share amount	0.00%
8 Percentage Points Below the Russell 2000 Index TSR
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of TSR target share amount	50.00%
Equal to the Russell 2000 Index TSR
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of TSR target share amount	100.00%
8 or More Percentage Points Above the Russell 2000 Index TSR
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of TSR target share amount	150.00%