Interim Consolidated Financial Information (Unaudited) (Details) (USD $) In Thousands, except Per Share data, 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
Interim Consolidated Financial Information (Unaudited)
Revenues	$ 113,845	$ 60,492	$ 86,542	$ 36,179	$ 28,889	$ 16,782	$ 16,811	$ 31,973	$ 297,059	$ 94,455	$ 169,878
Net income (loss)	$ 18,779	$ (21,710)	$ 4,037	$ (45,426)	$ (55,080)	$ (53,078)	$ (51,870)	$ (26,512)	$ (44,320)	$ (186,540)	$ (31,846)
Basic net income (loss) per share (in dollars per share)	$ 0.14	$ (0.17)	$ 0.03	$ (0.36)
Diluted net income (loss) per share (in dollars per share)	$ 0.14	$ (0.17)	$ 0.03	$ (0.36)
Shares used in computation of basic net income (loss) per share	131,711	130,851	129,224	127,203
Shares used in computation of diluted net income (loss) per share	139,118	130,851	137,969	127,203
Basic and diluted net loss per share (in dollars per share)					$ (0.44)	$ (0.42)	$ (0.41)	$ (0.21)	$ (0.34)	$ (1.49)	$ (0.26)
Shares used in computation of basic and diluted net loss per share					126,388	126,260	125,330	123,467	129,747	125,362	121,628