Share-Based Compensation - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2017 Plans shares	Jun. 30, 2016 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of share-based compensation plans | Plans	2
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock and restricted stock units granted	58,962	129,059
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock and restricted stock units granted	221,365	247,656