Restricted Shares Issued in Conjunction with Stock Plan (Detail) - Restricted Stock $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) shares
Period 1
Class of Stock [Line Items]
Issuance Date	Jan. 26, 2016
Shares | shares	43,220
Aggregate Market Value | $	$ 1.6
Period 2
Class of Stock [Line Items]
Issuance Date	Apr. 19, 2016
Shares | shares	800
Period 3
Class of Stock [Line Items]
Issuance Date	Jan. 30, 2017
Shares | shares	34,930
Aggregate Market Value | $	$ 1.6
Period 3 | Maximum
Class of Stock [Line Items]
Aggregate Market Value | $	$ 0.1
Period 4
Class of Stock [Line Items]
Issuance Date	Jan. 29, 2018
Shares | shares	37,510
Aggregate Market Value | $	$ 1.6