Investments - Amortized Cost and Fair Value of Securities Available for Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Available for sale:
Amortized Cost	$ 485,756	$ 182,325
Gross Unrealized Gains	2,675	178
Gross Unrealized Losses	(762)	(6,258)
Estimated Fair Value	487,669	176,245
Mortgage-backed securities
Available for sale:
Amortized Cost	215,888	159,937
Gross Unrealized Gains	1,895	155
Gross Unrealized Losses	(658)	(5,517)
Estimated Fair Value	217,125	154,575
Utah Housing Corporation bonds
Available for sale:
Amortized Cost	19,474	22,388
Gross Unrealized Gains	145	23
Gross Unrealized Losses	(83)	(741)
Estimated Fair Value	19,536	$ 21,670
U.S. government-sponsored enterprises
Available for sale:
Amortized Cost	250,394
Gross Unrealized Gains	635
Gross Unrealized Losses	(21)
Estimated Fair Value	$ 251,008

Amount, before tax, of unrealized gain 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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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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Amortized cost of 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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