Common Stock of the Company (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Class of Stock [Line Items]
Proceeds from Issuance of Common Stock	$ 382,063	$ 0
At Market Stock Offering Program Aggregate Value Of Common Stock	200,000
Common Stock, Shares, Issued	68,349,843		58,819,717
At Market Stock Offering Program Remained Available For Issuance	$ 187,000
Common Stock [Member]
Class of Stock [Line Items]
Issuance of common stock, shares	9,487,500
Common Stock [Member] | Issuance of Equity [Member]
Class of Stock [Line Items]
Issuance of common stock, shares	9,487,500
Common Stock [Member] | Issuance of Equity under ATM Program [Member]
Class of Stock [Line Items]
Issuance of common stock, shares	0
Common Stock, Shares, Issued	355,305