Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Accounts receivable, allowance	$ 1,052	$ 889
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	30,000,000	30,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common Stock [Member]
Common stock - Class A, par value	$ 0.01	$ 0.01
Common stock - Class A, shares authorized	400,000,000	400,000,000
Common stock - Class A, shares issued	128,228,000	129,134,000
Common stock - Class A, shares outstanding	128,228,000	129,134,000