Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
LIABILITIES AND STOCKHOLDERS' EQUITY
Accumulated amortization of deferred credit	$ 17,018	$ 13,123
Stockholders' equity:
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	2,500	2,500
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	60,000	60,000
Common stock, shares outstanding	39,780	39,398