CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 56,468	$ 49,645
Property, plant and equipment, accumulated depreciation	579,449	495,215
Intangible assets, accumulated amortization	$ 362,816	$ 271,568
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	1,000,000	1,000,000
Preferred stock, issued (in shares)	679,880	726,500
Preferred stock, outstanding (in shares)	679,880	726,500
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)	85,352,342	85,152,700
Common stock, outstanding (in shares)	85,352,342	85,152,700