CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 1,465	$ 1,306
Accumulated depreciation (in dollars)	$ 101,117	$ 96,554
Preferred stock, shares issued	0	0
Shares to be issued, shares	0	0
Common Class A
Common stock, shares issued	50,253,153	49,986,705
Common stock, shares outstanding	50,253,153	49,986,705
Common Class B
Common stock, shares issued	3,755	3,755
Common stock, shares outstanding	3,755	3,755