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Equity (Details) (USD $) | 3 Months Ended | 6 Months Ended | 9 Months Ended
--- | --- | --- | ---
Sep. 30, 2013 | Jun. 30, 2013 | Sep. 30, 2013 | Sep. 30, 2012
Statement of Equity [Abstract] |  |  |  |
stock offering | 11,100,000 |  |  |
Sale of Stock, Price Per Share | $ 28.54 |  | $ 28.54 |
Proceeds from Issuance of Common Stock | $ 20,000,000 | $ 47,000,000 | $ 67,000,000 | $ 0
Share Price | $ 29.50 |  | $ 29.50 |
Common Stock, Discount on Shares | 0.96 |  | 0.96 |
Equity Forward Sale Agreement, Settlement Threshold | 10,400,000 |  |  |
equity forward sale agreement future settlement amount | 291,000,000 |  |  |
Option Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value | $ 3,000,000 |  | $ 3,000,000 |
Net share settlement | 100,037 |  | 100,037 |

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- Details
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- Definition Discount on common shares, or any unamortized balance thereof, shown separately as a deduction from the applicable account(s) as circumstances require. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187103-122770 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 07 -Article 4 + Details
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