Federal Home Loan Bank Advances and Long-Term Debt - Schedule of Debt (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Short-Term Debt [Line Items]
Total FHLB advances	$ 3,000,000	$ 3,000,000
Weighted-average contractual interest rates for FHLB advances	3.87%	3.94%
Floating
Short-Term Debt [Line Items]
Total FHLB advances	$ 1,900,000	$ 2,000,000
Fixed
Short-Term Debt [Line Items]
Total FHLB advances	1,100,000	750,000
Overnight
Short-Term Debt [Line Items]
Total FHLB advances	$ 0	$ 250,000
Minimum | Floating
Short-Term Debt [Line Items]
Interest Rates	3.78%
Minimum | Fixed
Short-Term Debt [Line Items]
Interest Rates	3.87%
Maximum | Floating
Short-Term Debt [Line Items]
Interest Rates	3.88%
Maximum | Fixed
Short-Term Debt [Line Items]
Interest Rates	3.95%
Junior Subordinated Debt | MCBI Statutory Trust I
Short-Term Debt [Line Items]
Debt instrument, basis spread on variable rate	1.81%
Parent company | Junior Subordinated Debt
Short-Term Debt [Line Items]
Weighted-average rate (as a percent)	5.49%	5.53%
Long-term debt total	$ 32,400	$ 32,320