CONSOLIDATED STATEMENTS OF OTHER COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
CONSOLIDATED STATEMENTS OF OTHER COMPREHENSIVE INCOME
Net income (loss)	$ 28,573	$ 10,645	$ 6,272	$ (5,108)	$ 812	$ (21,313)	$ (10,713)	$ (19,536)	$ 40,382	$ (50,750)	$ (85,139)
Other comprehensive loss before tax:
Reduction of unrealized gain related to cash flow hedging instruments									(1,709)	(1,207)	(1,207)
Unrealized gain (loss) on marketable securities, available-for-sale:
Unrealized gain									1,217	360	1,750
Less: reclassification adjustments for gains included in net income (loss)									(233)	(1,358)	(2,558)
Total unrealized gains (losses) on marketable securities, available-for-sale									984	(998)	(808)
Other comprehensive loss before tax									(725)	(2,205)	(2,015)
Income tax benefit related to items of other comprehensive loss									653	502	771
Other comprehensive loss, net of tax									(72)	(1,703)	(1,244)
Comprehensive income (loss)									$ 40,310	$ (52,453)	$ (86,383)