Loans Held-for-Investment by Internal Risk Rating (Details) $ in Thousands	3 Months Ended
Jun. 30, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans (in number of loans) \| loan	121	120
Unpaid principal balance	$ 4,391,293	$ 4,257,145
Loans held-for-investment	$ 4,290,047	$ 4,226,212
Loans downgraded during the priod (in number of loans) \| loan	35
Unpaid principal balance of loans downgraded during the period	$ 1,500,000
Loans held-for investment, originated in current fiscal year	125,646
Loans held-for investment, originated in fiscal year before latest fiscal year	1,630,288
Loans held-for investment, originated two years before latest fiscal year	1,218,659
Loans held-for investment, originated three years before latest fiscal year	859,494
Loans held-for investment, originated four years before latest fiscal year	221,510
Loans held-for investment, originated five or more years before latest fiscal year	$ 234,450
Risk Rating 1 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans (in number of loans) \| loan	6	9
Unpaid principal balance	$ 173,494	$ 293,191
Loans held-for-investment	172,186	$ 292,270
Loans held-for investment, originated in current fiscal year	0
Loans held-for investment, originated in fiscal year before latest fiscal year	0
Loans held-for investment, originated two years before latest fiscal year	117,510
Loans held-for investment, originated three years before latest fiscal year	21,393
Loans held-for investment, originated four years before latest fiscal year	33,283
Loans held-for investment, originated five or more years before latest fiscal year	$ 0
Risk Rating 2 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans (in number of loans) \| loan	70	100
Unpaid principal balance	$ 2,508,630	$ 3,661,077
Loans held-for-investment	2,475,443	$ 3,632,528
Loans held-for investment, originated in current fiscal year	73,459
Loans held-for investment, originated in fiscal year before latest fiscal year	1,118,870
Loans held-for investment, originated two years before latest fiscal year	594,483
Loans held-for investment, originated three years before latest fiscal year	418,305
Loans held-for investment, originated four years before latest fiscal year	188,227
Loans held-for investment, originated five or more years before latest fiscal year	$ 82,099
Risk Rating 3 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans (in number of loans) \| loan	27	9
Unpaid principal balance	$ 890,835	$ 243,127
Loans held-for-investment	865,772	$ 241,901
Loans held-for investment, originated in current fiscal year	11,823
Loans held-for investment, originated in fiscal year before latest fiscal year	346,911
Loans held-for investment, originated two years before latest fiscal year	257,580
Loans held-for investment, originated three years before latest fiscal year	238,337
Loans held-for investment, originated four years before latest fiscal year	0
Loans held-for investment, originated five or more years before latest fiscal year	$ 11,121
Risk Rating 4 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans (in number of loans) \| loan	18	2
Unpaid principal balance	$ 818,334	$ 59,750
Loans held-for-investment	776,646	$ 59,513
Loans held-for investment, originated in current fiscal year	40,364
Loans held-for investment, originated in fiscal year before latest fiscal year	164,507
Loans held-for investment, originated two years before latest fiscal year	249,086
Loans held-for investment, originated three years before latest fiscal year	181,459
Loans held-for investment, originated four years before latest fiscal year	0
Loans held-for investment, originated five or more years before latest fiscal year	$ 141,230
Risk Rating 5 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans (in number of loans) \| loan	0	0
Unpaid principal balance	$ 0	$ 0
Loans held-for-investment	0	$ 0
Loans held-for investment, originated in current fiscal year	0
Loans held-for investment, originated in fiscal year before latest fiscal year	0
Loans held-for investment, originated two years before latest fiscal year	0
Loans held-for investment, originated three years before latest fiscal year	0
Loans held-for investment, originated four years before latest fiscal year	0
Loans held-for investment, originated five or more years before latest fiscal year	$ 0

Principal balance of loans with internal risk ratings downgraded during the period.

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Amount of financing receivable originated more than five years prior to current fiscal year.

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Amount, before allowance and fees, of loans and leases receivable. Excludes loans and leases covered under loss sharing agreements.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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