Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 56,691	$ 43,056
Restricted cash	3,117	3,106
Accounts receivable, net of allowance for doubtful accounts of $7,242 and $5,998 at September 30, 2018 and December 31, 2017, respectively	149,874	151,692
Inventory	27,478	18,654
Prepaid expenses	25,915	23,378
Other current assets	18,709	23,311
Total current assets	281,784	263,197
Property, plant, and equipment, net of accumulated depreciation of $209,120 and $171,395 at September 30, 2018 and December 31, 2017, respectively	343,281	373,123
Goodwill	300,909	236,555
Intangible assets, net of accumulated amortization of $92,437 and $67,588 at September 30, 2018 and December 31, 2017, respectively	466,740	403,493
Other assets	8,886	7,178
Total assets	1,401,600	1,283,546
Current liabilities:
Current portion of long-term debt	11,093	2,716
Accounts payable	13,152	15,750
Accrued expenses	97,728	97,027
Deferred revenue	103,449	88,164
Total current liabilities	225,422	203,657
Long-term liabilities:
Long-term debt	396,569	357,195
Deferred income taxes	9,928	8,080
Pension and other postretirement benefit obligations	23,557	25,462
Other long-term liabilities	16,290	14,759
Total liabilities	671,766	609,153
Redeemable noncontrolling interest	2,385	0
Stockholders’ equity:
Common stock, $0.01 par value, 2,000,000,000 shares authorized; 60,498,451 shares issued and 60,297,040 shares outstanding at September 30, 2018; 53,367,853 shares issued and 53,226,881 shares outstanding at December 31, 2017	605	534
Additional paid-in capital	738,881	683,168
Accumulated other comprehensive loss	(5,663)	(5,461)
Accumulated deficit	(4,509)	(2,767)
Treasury stock, at cost, 201,411 and 140,972 shares at September 30, 2018 and December 31, 2017, respectively	(1,865)	(1,081)
Total stockholders' equity	727,449	674,393
Total liabilities, redeemable noncontrolling interest and stockholders’ equity	$ 1,401,600	$ 1,283,546