Securities (Amortized Cost and Fair Value of Debt Securities Available for Sale) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Gross Amortized Cost	$ 7,190,161	$ 5,766,234
Securities Available for Sale, Gross Unrealized Gains	167,593	236,826
Securities Available for Sale, Gross Unrealized Losses	57,333	3,733
Securities Available for Sale, Fair Value	7,300,421	5,999,327
U.S. Treasury And Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Gross Amortized Cost	398,742	207,365
Securities Available for Sale, Gross Unrealized Gains	6,450	6,289
Securities Available for Sale, Gross Unrealized Losses	1,046	284
Securities Available for Sale, Fair Value	404,146	213,370
Municipal Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Gross Amortized Cost	306,803	309,342
Securities Available for Sale, Gross Unrealized Gains	14,912	17,536
Securities Available for Sale, Gross Unrealized Losses	2,420	153
Securities Available for Sale, Fair Value	319,295	326,725
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Gross Amortized Cost	3,457,426	2,560,249
Securities Available for Sale, Gross Unrealized Gains	44,662	69,570
Securities Available for Sale, Gross Unrealized Losses	30,538	8
Securities Available for Sale, Fair Value	3,471,550	2,629,811
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Gross Amortized Cost	2,865,057	2,323,306
Securities Available for Sale, Gross Unrealized Gains	96,868	135,516
Securities Available for Sale, Gross Unrealized Losses	23,329	3,288
Securities Available for Sale, Fair Value	2,938,596	2,455,534
Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Gross Amortized Cost	147,633	354,472
Securities Available for Sale, Gross Unrealized Gains	4,421	7,651
Securities Available for Sale, Fair Value	152,054	362,123
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Available for Sale, Gross Amortized Cost	14,500	11,500
Securities Available for Sale, Gross Unrealized Gains	280	264
Securities Available for Sale, Fair Value	$ 14,780	$ 11,764

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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Amount 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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