CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Accounts receivable, allowance for doubtful accounts	$ 19,896	$ 19,083
Property, plant and equipment, accumulated depreciation	402,113	364,124
Intangible assets, accumulated amortization	$ 136,251	$ 114,922
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	120,000,000	120,000,000
Common stock, issued (in shares)	84,942,134	84,883,517
Common stock, outstanding (in shares)	84,942,134	84,883,517
Series A preferred stock
Preferred stock, par value (in dollars per share)	$ 0.01
Preferred stock, authorized (in shares)	1,000,000
Preferred stock, issued (in shares)	770,000
Preferred stock, outstanding (in shares)	770,000