Amounts Charged to Expense for Stock-based Compensation (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation	$ 2,060		$ 1,467
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation	1,886		1,358
Directors restricted stock grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation	100	[1]	100	[1]
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation	$ 74		$ 9

[1] Relates to non-employee directors serving on the Parent Company's Board of Directors, all of whom have been elected by the Company's stockholders, as well as non-employee directors serving on NUAL's Board of Directors.