Summary of Stock Appreciation Rights Activity (Detail) (Stock Appreciation Rights [Member], USD $)	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Jul. 03, 2013	Dec. 31, 2012
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	170,000	170,000	170,000	170,000	170,000
Shares, Grants outstanding at end of the period	170,000	170,000	170,000	170,000	170,000	170,000
Shares, Grants exercisable at end of the period	82,291			18,958
Weighted Average Exercise Price per Share, Grants outstanding at beginning of the period	$ 18.18	$ 18.18	$ 18.18	$ 18.18	$ 18.18	$ 18.18
Weighted Average Exercise Price per Share, Grants outstanding at end of the period	$ 18.18	$ 18.18	$ 18.18	$ 18.18	$ 18.18	$ 18.18
Grants exercisable at end of the period	$ 17.75			$ 10.08