Share-based Compensation - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expenses	$ 0.6	$ 0.2	$ 1.3	$ 5.7
Total unrecognized cost for stock options	1.6		1.6
Unrecognized compensation cost, weighted average period of recognition			2 years
Restricted Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized cost for stock options	$ 0.2		$ 0.2
Unrecognized compensation cost, weighted average period of recognition			8 months