Balance Sheet Offsetting - Remaining Contractual Maturities of Repurchase Agreements by Class of Collateral Pledged (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	$ 602,106,000	$ 604,306,000
Debt Securities Issued by the U.S. Treasury and Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase		237,238,000
Debt Securities Issued by States and Political Subdivisions
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	590,000.0	2,790,000
Residential - Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	117,607,000	115,734,000
Residential - U.S. Government-Sponsored Enterprises
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	483,909,000	248,544,000
Maturity Up To 90 Days
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	1,516,000	1,200,000
Maturity Up To 90 Days | Debt Securities Issued by the U.S. Treasury and Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase		0
Maturity Up To 90 Days | Debt Securities Issued by States and Political Subdivisions
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	0	1,200,000
Maturity Up To 90 Days | Residential - Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	1,516,000	0
Maturity Up To 90 Days | Residential - U.S. Government-Sponsored Enterprises
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	0	0
Maturity 91 To 365 Days
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	100,000	2,616,000
Maturity 91 To 365 Days | Debt Securities Issued by the U.S. Treasury and Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase		0
Maturity 91 To 365 Days | Debt Securities Issued by States and Political Subdivisions
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	100,000	1,100,000
Maturity 91 To 365 Days | Residential - Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	0	1,516,000
Maturity 91 To 365 Days | Residential - U.S. Government-Sponsored Enterprises
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	0	0
Maturity 1 To 3 Years
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	25,000,000	225,000,000
Maturity 1 To 3 Years | Debt Securities Issued by the U.S. Treasury and Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase		199,173,000
Maturity 1 To 3 Years | Debt Securities Issued by States and Political Subdivisions
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	0	0
Maturity 1 To 3 Years | Residential - Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	22,158,000	25,827,000
Maturity 1 To 3 Years | Residential - U.S. Government-Sponsored Enterprises
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	2,842,000	0
Maturity After 3 Years
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	575,490,000	375,490,000
Maturity After 3 Years | Debt Securities Issued by the U.S. Treasury and Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase		38,065,000
Maturity After 3 Years | Debt Securities Issued by States and Political Subdivisions
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	490,000.0	490,000
Maturity After 3 Years | Residential - Government Agencies
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	93,933,000	88,391,000
Maturity After 3 Years | Residential - U.S. Government-Sponsored Enterprises
Securities Sold Under Agreements to Repurchase
Securities Sold under Agreements to Repurchase	$ 481,067,000	$ 248,544,000