Investment Securities (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Money market investments	$ 6,775	$ 4,930	$ 7,021
Securitized GNMA pools retained, amortized cost	$ 62,800	$ 56,800	$ 74,900
Securitized GNMA pool retained, yield	3.23%	3.93%	3.14%
Investments guaranteed by US treasury and sponsored agencies in unrealized loss on position	$ 317,100
Gain on sales of mortgaged-backed securities	8,300
Held-to-maturity, Amortized cost		$ 424,740
Carrying value of securities sold	672,192	17,837	$ 250,100
Sale of securities	8,274	0	6,896
Available-for-sale securities, acquired	$ 574,600
Available for sale securities average yield percent	1.79%
Available-for-sale term	1 year 6 months 18 days
Held-to-maturity Securities, Unrecognized Loss		14,387
Sale Price	$ 680,466	17,837	256,996
Government National Mortgage Association Certificates and Obligations (GNMA) [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying value of securities sold		$ 17,800	166,000
US Treasury Securities
Schedule of Available-for-sale Securities [Line Items]
Carrying value of securities sold			$ 84,100

Available For Sale Securities, Acquired

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Available for sale securities average yield percent

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As of the balance sheet date, the excess of carrying value (amortized cost) over fair value of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding loss.

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Investments in unrealized loss on positions guaranteed by US Treasury and sponsored agencies which are not subject to credit risk due to market conditions.

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Yield or cost of retained securitzed GNMA pools from its own origination.

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Loan pools securitized by GNMA at amortized cost.

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This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.

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Period between issuance and maturity of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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Net gain (loss) resulting from the sales of securitized, pay-through debt securities collateralized by real estate mortgage loans (mortgages).

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Amount, before other-than-temporary impairment (OTTI) accretion, of investment in debt securities measured at amortized cost (held-to-maturity).

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Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

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The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
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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.

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