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Debt (Summary of Additional Information of Credit facilities) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2015 | Sep. 30, 2014 | Sep. 30, 2015 | Sep. 30, 2014
Revolving Secured Line of Credit [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Maximum outstanding balance | $ 142.6 | $ 163.5 | $ 206.3 | $ 204.7
Average outstanding balance | 30.0 | 101.2 | 48.0 | 102.2
Warehouse Facility II [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Maximum outstanding balance | 200.8 | 290.2 | 200.8 | 290.2
Average outstanding balance | 4.4 | 152.9 | 10.6 | 89.6
Warehouse Facility IV [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Maximum outstanding balance | 12.0 | 26.7 | 35.0 | 26.7
Average outstanding balance | 12.0 | 24.5 | 8.2 | 21.7
Warehouse Facility V [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Maximum outstanding balance | 99.2 | 58.8 | 99.2 | 75.0
Average outstanding balance | 9.6 | 2.5 | 16.4 | 7.4
Warehouse Facility VI [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Maximum outstanding balance | 0.0 | 0.0 | 0.0 | 0.0
Average outstanding balance | $ 0.0 | $ 0.0 | $ 0.0 | $ 0.0

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