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Debt (Schedule of Additional Information Related to Debt Instruments) (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2017 | Mar. 31, 2016
Revolving Secured Line of Credit [Member] |  |
Debt Instrument [Line Items] |  |
Maximum outstanding balance | $ 188.0 | $ 186.4
Average outstanding balance | 62.4 | 56.6
Warehouse Facility II [Member] |  |
Debt Instrument [Line Items] |  |
Maximum outstanding balance | 200.1 | 200.1
Average outstanding balance | 4.5 | 4.4
Warehouse Facility IV [Member] |  |
Debt Instrument [Line Items] |  |
Maximum outstanding balance | 12.0 | 12.0
Average outstanding balance | 12.0 | 12.0
Warehouse Facility V [Member] |  |
Debt Instrument [Line Items] |  |
Maximum outstanding balance | 100.0 | 40.0
Average outstanding balance | 2.2 | 0.9
Warehouse Facility VI [Member] |  |
Debt Instrument [Line Items] |  |
Maximum outstanding balance | 49.9 | 14.7
Average outstanding balance | $ 1.1 | $ 8.9

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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Balance Type: | na
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- Definition Average amount borrowed under the credit facility during the period. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Maximum amount borrowed under the credit facility at any time during the period. + References No definition available. + Details
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- Details
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Balance Type: |
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- Details
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- Details
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- Details
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- Details
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Balance Type: |
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