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Shareholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Feb. 13, 2017	Feb. 12, 2017
Stockholders Equity [Line Items]
Cash dividends paid per share of Common and Class B common stock	$ 1.45	$ 1.05	$ 2.70	$ 2.10
Shares of non-vested restricted stock granted	8,500	55,500	100,109	155,899
Shares withheld as payment for tax withholdings related to share based compensation, market value			$ 2,213	$ 2,771
Stock options exercised, shares	9,501	2,250	44,584	16,000
Stock options exercised, proceeds	$ 1,369	$ 208	$ 3,981	$ 1,310
Common stock issued under employee stock purchase plan, shares	2,434	2,306	4,481	4,259
Common stock issued under employee stock purchase plan, net proceeds	$ 414	$ 317	$ 760	$ 602
Stock Options \| Common Stock
Stockholders Equity [Line Items]
Shares withheld to cover cost for stock option exercises related to share based compensation, shares	1,610		6,651
Shares withheld to cover cost for stock option exercises related to share based compensation, market value	$ 286		$ 1,200
Non-Vested Restricted Stock \| Common Stock
Stockholders Equity [Line Items]
Shares withheld as payment for tax withholdings related to share based compensation, shares	12,924	20,100	12,924	20,100
Shares withheld as payment for tax withholdings related to share based compensation, market value	$ 2,213	$ 2,771	$ 2,213	$ 2,771
Carrier Enterprise I
Stockholders Equity [Line Items]
Controlling interest, ownership percentage	80.00%		80.00%
Carrier Enterprise II
Stockholders Equity [Line Items]
Controlling interest, ownership percentage	80.00%		80.00%		80.00%	70.00%
Carrier Enterprise III
Stockholders Equity [Line Items]
Controlling interest, ownership percentage	60.00%		60.00%
401(k) Plan
Stockholders Equity [Line Items]
Common stock contribution to 401(k) Plan, shares			17,318	16,389
Common stock contribution to 401(k) Plan			$ 2,945	$ 2,428