Earnings Per Share - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share Basic [Line Items]
Weighted average restricted share units outstanding	523,000	455,000	492,000	375,000
Shares paid for tax withholding for share based compensation	9,673		25,380
Number of stock options dilutive shares included in the computation of EPS under the treasury stock method	264,537	179,640	267,818	230,605
Restricted Share Units
Earnings Per Share Basic [Line Items]
Weighted average share included in the computation of diluted EPS	85,808	57,591	76,595	47,810
Performance Share Units
Earnings Per Share Basic [Line Items]
Weighted average share included in the computation of diluted EPS	157,771	67,585	129,971	44,061
Stock Options
Earnings Per Share Basic [Line Items]
Number of stock options dilutive shares included in the computation of EPS under the treasury stock method	264,537	179,640	267,818	230,605
Anti-dilutive securities excluded from computation	841,058	872,406	841,058	851,752