Equity and Capital Equity and Capital - Common Stock (Details) (USD $)	9 Months Ended		3 Months Ended
	Sep. 30, 2012 Parent Company [Member]	Sep. 30, 2011 Parent Company [Member]	Sep. 30, 2012 Parent Company [Member] Common Stock [Member]	Sep. 30, 2012 Maximum	Aug. 10, 2012 Maximum
Class of Stock [Line Items]
Common Stock, Shares, Issued			442,786
Weighted Average Price Per Share			$ 49.70
Net proceeds from common stock issuance	$ 21,677,000	$ 215,369,000	$ 21,700,000
Payments of Stock Issuance Costs			300,000
Equity Issuance, Amount				$ 128,000,000	$ 150,000,000