Balance Sheet Offsetting - Remaining Contractual Maturities of Repurchase Agreements by Class of Collateral Pledged (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	$ 600,590	$ 604,306
Debt Securities Issued by States and Political Subdivisions
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	590	2,790
Residential - Government Agencies
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	103,809	115,734
Residential - U.S. Government-Sponsored Enterprises
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	496,191	248,544
Debt Securities Issued by the U.S. Treasury and Government Agencies
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase		237,238
Maturity Up To 90 Days
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	100	1,200
Maturity Up To 90 Days | Debt Securities Issued by States and Political Subdivisions
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	100	1,200
Maturity 91 To 365 Days
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase		2,616
Maturity 91 To 365 Days | Debt Securities Issued by States and Political Subdivisions
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase		1,100
Maturity 91 To 365 Days | Residential - Government Agencies
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase		1,516
Maturity 1 To 3 Years
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	575,000	225,000
Maturity 1 To 3 Years | Residential - Government Agencies
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	83,599	25,827
Maturity 1 To 3 Years | Residential - U.S. Government-Sponsored Enterprises
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	491,401
Maturity 1 To 3 Years | Debt Securities Issued by the U.S. Treasury and Government Agencies
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase		199,173
Maturity After 3 Years
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	25,490	375,490
Maturity After 3 Years | Debt Securities Issued by States and Political Subdivisions
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	490	490
Maturity After 3 Years | Residential - Government Agencies
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	20,210	88,391
Maturity After 3 Years | Residential - U.S. Government-Sponsored Enterprises
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	$ 4,790	248,544
Maturity After 3 Years | Debt Securities Issued by the U.S. Treasury and Government Agencies
Assets Sold Under Agreements To Repurchase [Line Items]
Securities Sold under Agreements to Repurchase		$ 38,065