CONSOLIDATED BALANCE SHEET (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Allowance for accounts receivable	$ 14,239	$ 11,489
Accumulated depreciation and amortization of property and equipment	287,526	271,811
Accumulated amortization of intangible assets	$ 94,027	$ 74,957
Treasury stock (shares)	194,163,000	194,163,000
Common stock $.001 par value; authorized 1,600,000 shares; issued 261,396 and 260,624 shares, respectively, and outstanding 77,601 and 76,829 shares, respectively
Par value of common stock (USD per share)	$ 0.001	$ 0.001
Common stock authorized (shares)	1,600,000,000	1,600,000,000
Common stock issued (shares)	261,936,000	260,624,000
Common stock outstanding (shares)	77,601,000	76,829,000
Class B convertible common stock $.001 par value; authorized 400,000 shares; issued 16,157 shares and outstanding 5,789 shares
Par value of common stock (USD per share)	$ 0.001	$ 0.001
Common stock authorized (shares)	400,000,000	400,000,000
Common stock issued (shares)	16,157,000	16,157,000
Common stock outstanding (shares)	5,789,000	5,789,000