Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating Activities
Net income	$ 56,732	$ 47,430
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7,513	7,417
Stock-based compensation	2,876	2,945
Loss (gain) on disposal of property, plant and equipment	1,343	(204)
Other non-cash adjustments	(405)	(285)
Changes in operating assets and liabilities:
Accounts receivable	(81,842)	(48,268)
Inventories	1,604	4,348
Prepaid expenses and other assets	3,701	(67)
Accounts payable	4,370	(161)
Accrued expenses and other liabilities	(5,680)	(7,901)
Income taxes receivable/payable	9,907	11,188
Net cash provided by operating activities	119	16,442
Investing Activities
Expenditures for property, plant and equipment	(7,125)	(5,182)
Proceeds from sales of property, plant and equipment		4,349
Net cash used in investing activities	(7,125)	(833)
Financing Activities
Borrowings under line of credit	163,000	194,000
Principal payments under line of credit	(163,000)	(158,000)
Repurchases of common stock	(3,271)	(54,703)
Financing costs		(485)
Proceeds from employee stock purchase and option plans	189	137
Net cash used in financing activities	(3,082)	(19,051)
Net decrease in cash and cash equivalents	(10,088)	(3,442)
Cash and cash equivalents, beginning of period	18,664	5,995
Cash and cash equivalents, end of period	8,576	2,553
Supplemental Disclosure:
Cash paid for interest	364	696
Cash paid for income taxes, net	$ 19,600	$ 13,982