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Shareholders Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 21, 2017
Stockholders Equity Note [Line Items]
Cash dividends paid per share of Common and Class B common stock	$ 1.05	$ 0.85	$ 2.10	$ 1.70
Shares of non-vested restricted stock granted	55,500	24,500	155,899	112,178
Common stock issued under employee stock purchase plan, shares	2,306	2,203	4,259	4,831
Common stock issued under employee stock purchase plan, net proceeds	$ 317	$ 287	$ 602	$ 584
Common Stock
Stockholders Equity Note [Line Items]
Stock options exercised, shares	2,250	7,500	16,000	34,500
Stock options exercised, proceeds	$ 208	$ 454	$ 1,310	$ 2,258
Carrier Enterprise I
Stockholders Equity Note [Line Items]
Controlling interest, ownership percentage	80.00%		80.00%		80.00%
Non-controlling interest, ownership percentage	20.00%		20.00%		20.00%
Carrier Enterprise II
Stockholders Equity Note [Line Items]
Controlling interest, ownership percentage	80.00%		80.00%
Non-controlling interest, ownership percentage	20.00%		20.00%
Carrier Enterprise III
Stockholders Equity Note [Line Items]
Controlling interest, ownership percentage	60.00%		60.00%
Non-controlling interest, ownership percentage	40.00%		40.00%
Non-Vested Restricted Stock \| Common Stock
Stockholders Equity Note [Line Items]
Shares withheld as payment for tax withholdings related to share based compensation, shares	20,100		20,100
Shares withheld as payment for tax withholdings related to share based compensation, market value	$ 2,771		$ 2,771
Non-Vested Restricted Stock \| Common Stock And Class B Common Stock
Stockholders Equity Note [Line Items]
Shares withheld as payment for tax withholdings related to share based compensation, shares		20,195		27,477
Shares withheld as payment for tax withholdings related to share based compensation, market value		$ 2,603		$ 3,548
401(k) Plan
Stockholders Equity Note [Line Items]
Common stock contribution to 401(k) Plan, shares			16,389	20,045
Common stock contribution to 401(k) plan			$ 2,428	$ 2,348