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Equity-Based Compensation (Narrative) (Details) (USD $) | 9 Months Ended | 12 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended | 9 Months Ended | 12 Months Ended |  |  | 12 Months Ended |  |  |  |
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Sep. 30, 2014 | Sep. 30, 2013 | Dec. 31, 2013 | Sep. 30, 2014 Former President and Chief Operating Officer | Sep. 30, 2014 2005 Equity Incentive Plan | Sep. 30, 2014 Performance Stock Units | Sep. 30, 2014 Management Stock Purchase Plan | Sep. 30, 2013 Management Stock Purchase Plan | Dec. 31, 2013 Management Stock Purchase Plan | Sep. 30, 2014 Minimum Performance Stock Units | Sep. 30, 2014 Maximum Performance Stock Units | Sep. 30, 2014 Unvested Restricted Stock Units | Dec. 31, 2013 Unvested Restricted Stock Units | Dec. 31, 2012 Awarded January 2012 Performance Stock Units | Sep. 30, 2014 Awarded January 2012 Performance Stock Units | Jan. 31, 2012 Awarded January 2012 Performance Stock Units | Dec. 31, 2013 Awarded January 2013 Performance Stock Units | Sep. 30, 2014 Awarded January 2013 Performance Stock Units | Jan. 31, 2013 Awarded January 2013 Performance Stock Units | Jan. 31, 2014 Awarded January 2014 Performance Stock Units | Sep. 30, 2014 Awarded June 2014 Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Typical vesting period, in years | 4 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum number of shares that may be issued under the Plan |  |  |  |  | 3,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum number of shares that may be issued in connection with grants of incentive stock options and rights |  |  |  |  | 900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Performance stock units outstanding |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 280,000 | 295,000 |  | 237,000 | 304,000 | 212,000 | 19,000
Performance stock unit grant-date fair value |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,152,000 |  |  | $ 4,123,000 | $ 3,914,000 | $ 319,000
Percentage of target performance stock units earned |  |  |  |  |  |  |  |  |  |  |  |  |  | 58.30% |  |  | 50.00% |  |  |  |
Performance stock units earned |  |  |  |  |  |  |  |  |  |  |  |  |  | 163,200 |  |  | 114,000 |  |  |  |
Performance stock units target awards |  |  |  |  |  |  |  |  |  |  |  |  |  | 280,000 |  |  | 237,000 |  |  |  |
Performance stock unit vesting period |  |  |  |  |  |  |  |  |  | 1 year | 3 years |  |  |  |  |  |  |  |  |  |
MSPP company matching portion, vesting age | 60 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Years of service |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Average closing price, number of days trailing |  |  |  |  |  | 90 days | 200 days |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accrues interest |  |  |  |  |  |  | 2.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of restricted stock units credited to participant accounts | 731,597 |  | 614,888 |  |  |  | 116,708 | 121,488 |  |  |  | 62,349 | 47,268 |  |  |  |  |  |  |  |
Weighted average fair value of per unit awarded |  |  |  |  |  |  | $ 16.73 |  | $ 15.97 |  |  |  |  |  |  |  |  |  |  |  |
Disbursements of MSPP |  | $ 531,000 |  | $ 2,120,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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