Fair Value Measurements (Financial Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2022		Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Values, Assets	$ 45,281		$ 6,908
Fair Values, Liabilities	3,796		22,244
Total recurring fair value measurements - liabilities	3,500		4,100
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities	5,993,007		6,986,698
Mortgage loans held for sale	25,046		41,022	[1]
Fair Values, Assets	59,658	[1]	75,867
Total fair value measurements	6,077,711		7,103,587
Fair Values, Liabilities	78,257	[1]	35,046
Total recurring fair value measurements - liabilities	78,257		35,046
Recurring [Member] | U.S. Treasury And Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities	9,631		419,298
Recurring [Member] | Municipal Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities	215,634		314,158
Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities	20,927		18,702
Recurring [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities	2,761,422		3,035,798
Recurring [Member] | Commercial Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities	2,894,173		3,077,859
Recurring [Member] | Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities	91,220		120,883
Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities	5,993,007		6,986,698
Mortgage loans held for sale	25,046		41,022	[1]
Fair Values, Assets	59,658	[1]	75,867
Total fair value measurements	6,077,711		7,103,587
Fair Values, Liabilities	74,741	[1]	30,930
Total recurring fair value measurements - liabilities	74,741		30,930
Recurring [Member] | Level 2 [Member] | U.S. Treasury And Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities	9,631		419,298
Recurring [Member] | Level 2 [Member] | Municipal Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities	215,634		314,158
Recurring [Member] | Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities	20,927		18,702
Recurring [Member] | Level 2 [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities	2,761,422		3,035,798
Recurring [Member] | Level 2 [Member] | Commercial Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities	2,894,173		3,077,859
Recurring [Member] | Level 2 [Member] | Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale debt securities	91,220		120,883
Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Values, Liabilities	3,516	[1]	4,116
Total recurring fair value measurements - liabilities	$ 3,516		$ 4,116

[1] For further disaggregation of derivative assets and liabilities, see Note 5 - Derivatives.