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Subsequent Event	3 Months Ended
Subsequent Event	Mar. 31, 2013
Subsequent Event [Abstract]
Subsequent Events [Text Block]	Subsequent Event In April 2013, the Company entered into Purchase and Sale Agreements related to the disposition of some of its non-core properties in the Northern Region for total consideration of $145.0 million before purchase price adjustments. The Company expects to record a gain on the sale of these assets of approximately $100.0 million and to close the transactions in the second quarter of 2013.