Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 7.75% senior notes	Dec. 31, 2013 7.75% senior notes	May 13, 2011 7.75% senior notes	Jun. 30, 2014 Class A common stock	Dec. 31, 2013 Class A common stock	Oct. 16, 2013 Class A common stock	Jun. 30, 2014 Class B common stock	Dec. 31, 2013 Class B common stock	Jun. 30, 2014 Class C common stock	Dec. 31, 2013 Class C common stock
Condensed Financial Statements, Captions [Line Items]
Allowance for doubtful accounts	$ 5,305	$ 5,306
Treasury stock, shares	22,585,795	24,205,200
Interest on borrowings, per annum			7.75%	7.75%	7.75%
Common stock, par value (in dollars per share)						$ 0.01	$ 0.01		$ 0.01	$ 0.01	$ 0.01	$ 0.01
Common stock, shares authorized						750,000,000	750,000,000		600,000,000	600,000,000	644,871	644,871
Common stock, shares issued						253,776,605	222,399,019	18,860,000	0	15,424,944	644,871	644,871
Common stock, shares outstanding						231,190,810	198,193,819		0	15,424,944	644,871	644,871