Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Activities:
Net income	$ 95,393	$ 70,119	$ 35,133
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	31,029	35,029	31,249
Deferred income taxes	(711)	(11,103)	(2,121)
Gain on CRS settlement	(9,949)
Revaluation of derivatives	(490)	(1,039)	(2,678)
Debt extinguishment expenses		1,370
Stock compensation	6,018	4,652	2,636
Loss on sale of property and equipment	20	131	106
Loss from write-off of intangible assets	358
Provision for doubtful accounts	115	1,017	(705)
Defined benefit pension plan expense	668	820	(659)
Gain from equity investment		(785)	(436)
Changes in operating assets and liabilities:
Accounts receivable	(12,399)	(16,902)	(13,828)
Inventory	(10,954)	(8,367)	(9,600)
Prepaid expenses and other assets	(11,122)	(5,871)	(9,446)
Accounts payable	8,049	6,956	18,255
Accrued liabilities	8,687	4,308	11,888
Net cash provided by operating activities	104,712	80,335	59,794
Investing Activities:
Settlement of derivative financial instruments	(7,593)
Purchase of non-controlling interest			(48,567)
Investment in subsidiary, net of cash acquired	107	(31,474)
Cash invested in corporate owned life insurance			(266)
Purchases of property and equipment	(55,490)	(38,887)	(35,861)
Proceeds from the sale of property and equipment	248	487	11
Net cash used in investing activities	(62,728)	(69,874)	(84,683)
Financing Activities:
Distribution paid to non-controlling interest			(3)
Cash paid for financing costs		(1,139)
Borrowing of Debt	15,000	91,592	45,669
Repayments of Debt	(5,053)	(79,692)	(24,496)
Cash paid for the cancellation of restricted stock	(1,475)	(1,113)
Excess tax benefit from equity awards	6,681	1,831	2,074
Redemption of Series C Preferred Stock			(8,446)
Series C Preferred Stock Holders dividend			(696)
Proceeds from the exercise of Common Stock options	9,273	7,176	4,801
Net cash provided by financing activities	24,426	18,655	18,903
Foreign currency effect on cash and cash equivalents	(7,631)	1,699	2,719
Net increase (decrease) in cash and cash equivalents	58,779	30,815	(3,267)
Cash and cash equivalents at beginning of period	85,700	54,885	58,152
Cash and cash equivalents at end of period	144,479	85,700	54,885
Supplemental disclosure of cash flow information:
Cash paid for interest	2,826	2,558	2,653
Cash paid for taxes	32,376	21,756	11,326
Supplemental disclosure of non-cash transactions:
Issuance of Common Stock to non-controlling interest			42,517
Issuance of Common Stock for Series C Preferred Stock conversion			15,108
Capital Lease			3,254
Common Stock issued to directors and employees	$ 3,734	$ 2,706	$ 1,509