Shareholders Equity (Narrative) (Details) (USD $)
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12 Months Ended | 12 Months Ended | ||||||||||||||
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2013
At The Market Equity Program [Member]
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Dec. 31, 2012
At The Market Equity Program [Member]
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May 08, 2012
At The Market Equity Program [Member]
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Dec. 31, 2013
Common Stock [Member]
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Dec. 31, 2012
Common Stock [Member]
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Dec. 31, 2011
Common Stock [Member]
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Dec. 31, 2013
5.417% Series 1 Cumulative Convertible Preferred [Member]
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Dec. 31, 2012
5.417% Series 1 Cumulative Convertible Preferred [Member]
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Dec. 31, 2011
5.417% Series 1 Cumulative Convertible Preferred [Member]
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Dec. 31, 2013
Commissions [Member]
At The Market Equity Program [Member]
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Dec. 31, 2012
Commissions [Member]
At The Market Equity Program [Member]
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Dec. 31, 2013
Other Offering Costs [Member]
At The Market Equity Program [Member]
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Dec. 31, 2012
Other Offering Costs [Member]
At The Market Equity Program [Member]
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Shares issued under dividend reinvestment plan (in shares) | 20,026 | 22,814 | 28,823 | 20,026 | 22,814 | 28,823 | ||||||||||
Preferred shares, shares outstanding | 399,896 | 399,896 | 399,896 | |||||||||||||
Preferred Shares, percentage | 5.417% | 5.417% | 5.417% | |||||||||||||
Preferred Stock, Liquidation Preference Per Share | $ 25 | $ 25 | $ 25 | |||||||||||||
Common Stock, Shares, Issued | 66,701,422 | 64,815,446 | ||||||||||||||
Preferred shares, par | $ 0.01 | $ 0.01 | $ 0.01 | |||||||||||||
Convertible Preferred Stock, Converstion Price Per Share | $ 104.69 | |||||||||||||||
Aggregate offering price of common share | $ 300,000,000 | |||||||||||||||
Shares issued under equity program | 1,734,974 | 1,040,946 | 1,735,089 | 1,039,405 | 1,662,230 | |||||||||||
Weighted average price per common share | $ 108.01 | $ 103.69 | ||||||||||||||
Net cash proceeds of common stock | 186,548,000 | 112,270,000 | 154,921,000 | 185,200,000 | 106,400,000 | |||||||||||
Commissions related to sales of common shares | 2,000,000 | 1,400,000 | 200,000 | 200,000 | ||||||||||||
Remaining Capacity To Issue | $ 26,000,000 |