Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		1 Months Ended	3 Months Ended	4 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	May 10, 2013 At The Market Stock Issues [Member]	Mar. 31, 2013 At The Market Stock Issues [Member]	May 10, 2013 At The Market Stock Issues [Member]	Mar. 01, 2013 At The Market Stock Issues [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		0
Denominator - basic (in shares)	161,540,000	148,495,000
Deemed shares related to deferred compensation arrangements (in shares)	0	43,000
Denominator - diluted (in shares)	161,540,000	148,538,000
Class of Stock Disclosures [Abstract]
Common Stock Offering, Maximum Aggregate Price			$ 227,774		$ 227,774	$ 300,000
Commission To Sales Agent, Percent						2.00%
Stock Issued During Period Shares New Issues Including Shares Settled Subsequent To The End Of Period				2,668,438
Common Stock, Shares, Issued			394,000	1,899,105	3,062,438
Proceeds From Issuance Of Common Stock, Price Per Share, Weighted Average			$ 23.59	$ 23.58	$ 23.59
Proceeds From Issuance Of Common Stock Gross Including Subsequent Settlements				62,933
Stock Issued During Period Value New Issues Including Subsequent Settlements				62,146
Proceeds From Issuance Of Common Stock, Gross			9,293	44,459
Issuance of common stock	$ 43,869		$ 9,177	$ 43,904