Subsequent Event (Details Textual) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Jan. 03, 2012
Subsequent Event (Textual) [Abstract]
Acquisition Date		January 3, 2012
Total consideration of completed acquisition			$ 346,073,000
Estimated acquisition-related costs		9,200,000
Acquisition-related costs recognized		900,000
Acquisition-related costs to be recognized	8,300,000
Selling, general and administrative expenses related to accelerated vesting of stock options	4,500,000
Gain to be recognized from re-measurement of pre-acquisition equity interest to estimated fair value	5,800,000
Tax benefit due to release of valuation allowance resulting from net deferred tax liabilities created from acquisition	41,700,000
Griffin Project [Member]
Business Acquisition [Line Items]
Expected costs to complete		$ 34,000,000
Discount rate applied to project		17.40%