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Debt (Summary of Additional Information of Credit facilities) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2015 | Jun. 30, 2014 | Jun. 30, 2015 | Jun. 30, 2014
Revolving Secured Line of Credit [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Maximum outstanding balance | $ 51.2 | $ 201.5 | $ 206.3 | $ 204.7
Average outstanding balance | 6.9 | 124.6 | 57.1 | 102.7
Warehouse Facility II [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Maximum outstanding balance | 0.0 | 162.6 | 190.0 | 162.6
Average outstanding balance | 0.0 | 56.5 | 13.8 | 57.5
Warehouse Facility IV [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Maximum outstanding balance | 12.0 | 26.5 | 35.0 | 26.6
Average outstanding balance | 6.2 | 24.5 | 6.3 | 20.2
Warehouse Facility V [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Maximum outstanding balance | 29.0 | 69.1 | 75.0 | 75.0
Average outstanding balance | $ 24.3 | $ 11.4 | $ 19.8 | $ 9.9

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