CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Cash Flows from Operating Activities:
Net income	$ 48,111	$ 46,827	$ 42,681
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	10,453	8,961	8,092
Stock-based compensation expense	1,049	994	929
Provision for doubtful accounts	360	1,097	1,383
Deferred income taxes	3,506	2,652	1,212
Loss on disposal of fixed assets	92	44	14
Excess tax benefit from exercise of equity awards	(513)	(552)	(556)
Changes in assets and liabilities:
Accounts receivable	(33,835)	(64,215)	(11,359)
Inventories	12,401	(11,863)	(11,776)
Prepaid expenses and other current assets	(1,274)	(285)	1,829
Other non-current assets	(321)	(328)	(4)
Accounts payable	(3,012)	41,324	202
Accrued expenses and other liabilities	(3,431)	6,206	2,751
Net cash provided by operating activities	33,586	30,862	35,398
Cash Flows from Investing Activities:
Cash paid for Acquisitions	(42,990)
Purchases of property and equipment	(11,885)	(12,337)	(7,609)
Purchase of intangible asset		(450)
Proceeds from sale of equipment			13
Net cash used for investing activities	(54,875)	(12,787)	(7,596)
Cash Flows from Financing Activities:
Dividend payment	(10,591)		(10,527)
Issuance of stock under Employee Stock Purchase Plan	961	875	753
Excess tax benefit from exercise of equity awards	513	552	556
Exercise of stock options	135	437	356
Payment of payroll taxes on stock-based compensation through shares withheld	(737)	(660)	(578)
Net cash (used for) provided by financing activities	(9,719)	1,204	(9,440)
(Decrease) increase in cash and cash equivalents	(31,008)	19,279	18,362
Cash and cash equivalents, beginning of year	80,188	60,909	42,547
Cash and cash equivalents, end of year	49,180	80,188	60,909
Non-cash Investing and Financing Activities:
Accrued capital expenditures	109	504	205
Dividend declaration	9,041	10,591
Supplemental Cash Flow Information:
Income taxes paid	$ 29,740	$ 30,371	$ 24,219