Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Condensed Consolidated Balance Sheets
Receivables, allowance for doubtful accounts (in dollars)	$ 3,909	$ 3,901
Debt issuance costs, accumulated amortization (in dollars)	$ 13,548	$ 11,462
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	12,050	12,275
Preferred stock, shares outstanding	12,050	12,275
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	78,175,181	77,446,601