Number 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
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of dilutive EPS	986	2,295
Stock options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of dilutive EPS	986	2,221
Restricted share awards
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of dilutive EPS		74