Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Allowance for doubtful accounts receivable	$ 2,957	$ 2,241
Accumulated amortization of finite-lived intangible assets	$ 536,929	$ 416,708
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	100,000,000
Common stock, shares issued	96,552,226	82,268,722
Common stock, shares outstanding	95,765,787	81,482,283
Common stock, shares unvested	12,438	17,188
Treasury stock, shares	786,439	786,439
Class A Non-Voting Common Stock [Member]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	5,000,000	5,000,000
Common stock, shares issued	2,703,846	2,703,846
Common stock, shares outstanding	2,703,846	2,703,846