CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Sep. 30, 2011	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2010
CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY [Abstract]
Offering costs in conjunction with common stock offering	$ 10,600	$ 14,600	$ 25,200	$ 22,471

The cash outflow for cost incurred directly with the issuance of an equity security.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 18, 19, 20

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3291-108585

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