Investment Securities - Schedule of Unrealized Losses and Estimated Fair Values (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Estimated Fair Value, Less Than 12 Months	$ 3,755	$ 166,470
Available For Sale Securities Continuous Unrealized Income Loss Position Less Than Twelve Months Aggregate Gain Losses	(10)	(637)
Estimated Fair Value, 12 Months or More	0	235,380
SecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLosses	0	(2,950)
Securities Continuous Unrealized Loss Position Fair Value	3,755	401,850
SecuritiesContinuousUnrealizedLossPositionAggregateLosses	(10)	(3,587)
Mortgage - Backed Securities - Residential [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Estimated Fair Value, Less Than 12 Months	3,755	111,969
Available For Sale Securities Continuous Unrealized Income Loss Position Less Than Twelve Months Aggregate Gain Losses	(10)	(436)
Estimated Fair Value, 12 Months or More	0	219,015
SecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLosses	0	(2,801)
Securities Continuous Unrealized Loss Position Fair Value	3,755	330,984
SecuritiesContinuousUnrealizedLossPositionAggregateLosses	$ (10)	(3,237)
Mortgage - Backed Securities - Commercial [Member] | Obligations of U.S. Government [Member]
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Estimated Fair Value, Less Than 12 Months		54,501
Available For Sale Securities Continuous Unrealized Income Loss Position Less Than Twelve Months Aggregate Gain Losses		(201)
Estimated Fair Value, 12 Months or More		16,365
SecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLosses		(149)
Securities Continuous Unrealized Loss Position Fair Value		70,866
SecuritiesContinuousUnrealizedLossPositionAggregateLosses		$ (350)