Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating activities
Net income	$ 16,174	$ 26,100
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation expense	35,603	31,705
Amortization of intangible assets	8,936	3,416
Stock-based compensation expense	3,421	3,780
Pension and postretirement	(448)	(2,892)
Excess tax (deficiency) / benefit from stock-based compensation	140	(1,391)
Amortization of debt issuance costs	1,124	1,007
(Gain) / loss on disposal of fixed assets	(62)	178
Deferred income taxes	1,064	1,864
Change in fair value of contingent consideration liability	1,526
Changes in assets and liabilities:
Trade accounts receivable, net	(8,169)	(26,695)
Other receivables	1,789	(946)
Inventories	847	(17,178)
Prepaid expenses and other current assets	8,007	(9,642)
Other assets		(216)
Accounts payable	7,936	(51)
Accrued expenses and other liabilities	(6,303)	(1,842)
Accrued compensation costs	(15,320)	(16,479)
Accrued income taxes	2,340	5,370
Net cash provided by (used in) operating activities	58,605	(3,912)
Investing activities
Purchase of intangible assets	(500)
Capital expenditures	(36,163)	(28,762)
Proceeds from the sale of assets	4,856
Net cash used in investing activities	(31,807)	(28,762)
Financing activities
Proceeds from revolving credit facility	134,600	86,400
Repayments on revolving credit facility	(131,000)	(76,400)
Proceeds from receivables credit facility	6,670	12,962
Repayments on receivables credit facility	(24,700)	(4,962)
Payment of loan amendment fees	(2,250)
Proceeds from other current borrowings		6,615
Cash dividend paid	(9,696)	(9,838)
Payment of withholding taxes on vested stock awards	(692)	(2,322)
Proceeds from exercises of stock options	209	491
Proceeds from shares issued to ESPP	464	415
Excess tax benefit from stock-based compensation		1,391
Excess tax deficiency from stock-based compensation	(140)
Net cash (used in) provided by financing activities	(26,535)	14,752
Net increase (decrease) in cash and cash equivalents	263	(17,922)
Cash and cash equivalents-beginning of period	6,821	28,467
Cash and cash equivalents-end of period	$ 7,084	$ 10,545