Investment Securities - Schedule of AFS Debt Securities in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 2,382,336	$ 318,953
Less Than 12 Months, Gross Unrealized Losses	(41,157)	(1,499)
12 Months or Longer, Fair Value	114,536	165,159
12 Months or Longer, Gross Unrealized Losses	(1,480)	(876)
Total Fair Value	2,496,872	484,112
Total Gross Unrealized Losses	(42,637)	(2,375)
Debt Securities Issued by the U.S. Treasury and Government Agencies
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value	888	21,338
Less Than 12 Months, Gross Unrealized Losses	(5)	(42)
12 Months or Longer, Fair Value	17,724	87,070
12 Months or Longer, Gross Unrealized Losses	(136)	(549)
Total Fair Value	18,612	108,408
Total Gross Unrealized Losses	(141)	(591)
Debt Securities Issued by States and Political Subdivisions
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value	314
Less Than 12 Months, Gross Unrealized Losses	(1)
12 Months or Longer, Fair Value		26
12 Months or Longer, Gross Unrealized Losses		(1)
Total Fair Value	314	26
Total Gross Unrealized Losses	(1)	(1)
Debt Securities Issued by Government-Sponsored Enterprises
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value	64
Less Than 12 Months, Gross Unrealized Losses	(1)
Total Fair Value	64
Total Gross Unrealized Losses	(1)
Debt Securities Issued by Corporations
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value	49,813	65,000
Less Than 12 Months, Gross Unrealized Losses	(187)	(853)
12 Months or Longer, Fair Value	88,832	50,000
12 Months or Longer, Gross Unrealized Losses	(1,168)	(103)
Total Fair Value	138,645	115,000
Total Gross Unrealized Losses	(1,355)	(956)
Residential - Government Agencies
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value	678,445	113,538
Less Than 12 Months, Gross Unrealized Losses	(13,648)	(222)
12 Months or Longer, Fair Value	7,980	28,063
12 Months or Longer, Gross Unrealized Losses	(176)	(223)
Total Fair Value	686,425	141,601
Total Gross Unrealized Losses	(13,824)	(445)
Residential - U.S. Government-Sponsored Enterprises
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value	1,628,682	94,002
Less Than 12 Months, Gross Unrealized Losses	(26,765)	(324)
Total Fair Value	1,628,682	94,002
Total Gross Unrealized Losses	(26,765)	(324)
Commercial - Government Agencies
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value	24,130	25,075
Less Than 12 Months, Gross Unrealized Losses	(550)	(58)
Total Fair Value	24,130	25,075
Total Gross Unrealized Losses	(550)	(58)
Mortgage-Backed Securities
Schedule Of Available For Sale Securities [Line Items]
Less Than 12 Months, Fair Value	2,331,257	232,615
Less Than 12 Months, Gross Unrealized Losses	(40,963)	(604)
12 Months or Longer, Fair Value	7,980	28,063
12 Months or Longer, Gross Unrealized Losses	(176)	(223)
Total Fair Value	2,339,237	260,678
Total Gross Unrealized Losses	$ (41,139)	$ (827)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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