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Forward Equity Sale Agreement	12 Months Ended
	Dec. 31, 2012
Forward Equity Sale Agreement
Forward Equity Sale Agreement	13.   Forward Equity Sale Agreement         In August 2012, the Company amended its forward equity agreement to increase the amount of shares of common stock it may sell to an aggregate of $400.0 million. During 2012, the Company entered into contracts to sell a notional amount of $147.2 million at an average share price of $121.37. The Company has the ability to settle the contracts either by delivering shares of common stock and receiving cash or net settling for cash or shares of common stock. All contracts remain outstanding.

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Information about forward equity sale agreements, which may include amounts outstanding and capacity to sell.

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