Significant Accounting Policies - Schedule of Antidilutive Securities (Detail) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Director stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	4	0
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	11	0
Performance share units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	78	14
Restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	77	25