CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current Assets:
Allowance for doubtful accounts on trade accounts receivable - other	$ 17,955	$ 22,167
Common stock, par value (in dollars per share)	$ 86.08
Class A common stock
Current Assets:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	1,600,000,000	1,600,000,000
Common stock, shares issued	226,812,205	281,866,884
Common stock, shares outstanding	226,812,205	225,748,624
Class B common stock
Current Assets:
Common stock, par value (in dollars per share)	$ 0.01
Common stock, shares authorized	800,000,000	800,000,000
Common stock, shares issued	238,435,208	238,435,208
Common stock, shares outstanding	238,435,208	238,435,208