CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 3.50% Senior Convertible Notes due 2027	Dec. 31, 2010 3.50% Senior Convertible Notes due 2027
Other property and equipment, accumulated depreciation (in dollars)	$ 23,985	$ 15,480
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized shares	200,000,000	200,000,000
Common stock, issued shares	64,079,885	63,412,800
Common stock, outstanding, net of treasury shares	63,998,818	63,310,165
Treasury stock, shares	81,067	102,635
Interest rate on notes (as a percent)			3.50%	3.50%
Senior Convertible Notes, unamortized discount (in dollars)			$ 4,861	$ 11,827