CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 1,207	$ 1,409
Accumulated depreciation (in dollars)	$ 104,068	$ 95,083
Preferred stock, shares issued	0	0
Shares to be issued, shares	0	0
Common Class A
Common stock, shares issued	49,935,095	49,680,109
Common stock, shares outstanding	49,935,095	49,680,109
Common Class B
Common stock, shares issued	3,755	3,755
Common stock, shares outstanding	3,755	3,755