Residential Mortgage Securities and MSR-Related Assets (Unrealized Losses) (Details) $ in Thousands	Jun. 30, 2020 USD ($) security	Dec. 31, 2019 USD ($)
Fair Value
Less than 12 Months	$ 102,899
12 Months or more	0
Total	102,899
Unrealized Losses
Less than 12 Months	9,675
12 Months or more	0
Total	$ 9,675
Number of Securities
Less than 12 months (in security) \| security	13
12 months or more (in security) \| security	0
Available-for-sale securities	$ 148,343	$ 3,983,519
Gross unrealized losses	9,675	18,818
Non-Agency MBS
Fair Value
Less than 12 Months	43,422
12 Months or more	0
Total	43,422
Unrealized Losses
Less than 12 Months	6,372
12 Months or more	0
Total	$ 6,372
Number of Securities
Less than 12 months (in security) \| security	5
12 months or more (in security) \| security	0
Available-for-sale securities	$ 54,237	2,063,529
Gross unrealized losses	6,372	18
Expected to Recover Par
Fair Value
Less than 12 Months	43,422
12 Months or more	0
Total	43,422
Unrealized Losses
Less than 12 Months	6,372
12 Months or more	0
Total	$ 6,372
Number of Securities
Less than 12 months (in security) \| security	5
12 months or more (in security) \| security	0
Available-for-sale securities	$ 51,672	725,668
Gross unrealized losses	6,372	9
Total MBS
Fair Value
Less than 12 Months	43,422
12 Months or more	0
Total	43,422
Unrealized Losses
Less than 12 Months	6,372
12 Months or more	0
Total	$ 6,372
Number of Securities
Less than 12 months (in security) \| security	5
12 months or more (in security) \| security	0
Available-for-sale securities		3,728,111
Gross unrealized losses		18,727
CRT securities
Fair Value
Less than 12 Months	$ 59,477
12 Months or more	0
Total	59,477
Unrealized Losses
Less than 12 Months	3,303
12 Months or more	0
Total	$ 3,303
Number of Securities
Less than 12 months (in security) \| security	8
12 months or more (in security) \| security	0
Available-for-sale securities	$ 94,106	255,408
Gross unrealized losses	3,303	$ 91
CRT in Loss Positions Only, Fair Value Option
Number of Securities
Available-for-sale securities	59,500
Gross unrealized losses	$ 3,300

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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