Summary of Stock Appreciation Rights Activity (Detail) (Stock Appreciation Rights [Member], USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended		12 Months Ended
	Nov. 30, 2012	Aug. 31, 2012	Dec. 31, 2014	Dec. 31, 2012	Dec. 31, 2013
Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Grants outstanding at beginning of the period			170,000
Shares, Granted	100,000	70,000		170,000
Shares, Grants outstanding at end of the period			170,000	170,000
Shares, Grants exercisable at end of the period			92,916		50,416
Shares, Grants vested and expected to vest at end of the period			170,000	170,000	170,000
Weighted Average Exercise Price per Share, Grants outstanding at beginning of the period			$ 18.18
Weighted Average Exercise Price per Share, Granted				$ 18.18
Weighted Average Exercise Price per Share, Grants outstanding at end of the period			$ 18.18	$ 18.18
Weighted Average Exercise Price per Share, Grants exercisable at end of the period			$ 17.80		$ 17.48
Weighted Average Exercise Price per Share, Grants vested and expected to vest at end of the period			$ 18.18	$ 18.18	$ 18.18
Stock Appreciation Rights, Aggregate Intrinsic Value
SARs outstanding at December 31, 2014			$ 307
SARs exercisable at December 31, 2014			179
SARs vested and expected to vest at December 31, 2014			$ 307
Stock Appreciation Rights, Weighted Average Remaining Contractual Life
SARs outstanding at December 31, 2014			7 years 9 months 4 days
SARs exercisable at December 31, 2014			7 years 9 months 4 days
SARs vested and expected to vest at December 31, 2014			7 years 9 months 4 days