Debt Securities - Credit Quality Indicators for HTM Debt Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt securities, held-to-maturity	$ 189,836	$ 224,611
US States and Political Subdivisions Debt Securities
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt securities, held-to-maturity	189,836	224,611
Moody's, Aaa Rating | Standard & Poor's, AAA Rating | US States and Political Subdivisions Debt Securities | Internal Investment Grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt securities, held-to-maturity	39,022	65,217
Moody's, Aa1, Aa2 or Aa3 Ratings | Standard & Poor's, AA+, AA or AA- Ratings | US States and Political Subdivisions Debt Securities | Internal Investment Grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt securities, held-to-maturity	123,664	130,316
Moody's, A1, A2 or A3 Ratings | Standard & Poor's, A+, A or A- Ratings | US States and Political Subdivisions Debt Securities | Internal Investment Grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt securities, held-to-maturity	27,150	28,689
Moody's, Not Rated | Standard & Poor's, Not Rated | US States and Political Subdivisions Debt Securities | Internal Investment Grade
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt securities, held-to-maturity	$ 0	$ 389