Fair Value - Financial Assets and Liabilities Measured at Fair Value Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	$ 3,018,246	$ 3,238,877
Loans held for sale	222,538	275,706
Mortgage servicing rights (MSR)	111,050	87,687	$ 83,035	$ 66,464
U.S. Government Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	12,623	13,727
Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	5,359	5,714
Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	3,018,246	3,238,877
Loans held for sale	222,538	275,706
Mortgage servicing rights (MSR)	111,050	87,687
Other assets - derivatives	6,602	24,809
Other liabilities - derivatives	21,892	4,677
Recurring Basis [Member] | U.S. Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	361,822	344,640
Recurring Basis [Member] | U.S. Government Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	12,623	13,727
Recurring Basis [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	5,359	5,714
Recurring Basis [Member] | Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,638,442	2,874,796
Level 1 [Member] | Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	361,822	344,640
Loans held for sale	0	0
Mortgage servicing rights (MSR)	0	0
Other assets - derivatives	1,906	2,794
Other liabilities - derivatives	10,537	414
Level 1 [Member] | Recurring Basis [Member] | U.S. Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	361,822	344,640
Level 1 [Member] | Recurring Basis [Member] | U.S. Government Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Level 1 [Member] | Recurring Basis [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Level 1 [Member] | Recurring Basis [Member] | Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Level 2 [Member] | Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,656,424	2,894,237
Loans held for sale	222,538	275,706
Mortgage servicing rights (MSR)	0	0
Other assets - derivatives	5,216	20,156
Other liabilities - derivatives	11,355	4,263
Level 2 [Member] | Recurring Basis [Member] | U.S. Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Level 2 [Member] | Recurring Basis [Member] | U.S. Government Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	12,623	13,727
Level 2 [Member] | Recurring Basis [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	5,359	5,714
Level 2 [Member] | Recurring Basis [Member] | Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,638,442	2,874,796
Level 3 [Member] | Recurring Basis [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Loans held for sale	0	0
Mortgage servicing rights (MSR)	111,050	87,687
Other assets - derivatives	520	1,859
Other liabilities - derivatives	0	0
Level 3 [Member] | Recurring Basis [Member] | U.S. Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Level 3 [Member] | Recurring Basis [Member] | U.S. Government Agency Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Level 3 [Member] | Recurring Basis [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Level 3 [Member] | Recurring Basis [Member] | Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	$ 0	$ 0