Effect of Stock Options and Restricted Share Awards that were Issued or Outstanding but were Excluded in Calculating Diluted Earnings Per Share Because their Effect would have been Anti-Dilutive (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of dilutive EPS	733	2,186	751	2,217
Stock options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of dilutive EPS	691	2,185	724	2,213
Restricted share awards
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of dilutive EPS	42	1	27	4