Securities - Schedule of Securities in a Continuous Unrealized Loss Position Aggregated by Investment Category and Length of Time (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Less than 12 months, Fair Value	$ 3,930	$ 39,135
Less than 12 months, Unrealized Loss	(70)	(305)
12 months or more, Fair Value	363,097	394,686
12 months or more, Unrealized Loss	(8,817)	(15,616)
Total, Fair Value	367,027	433,821
Total, Unrealized Loss	(8,887)	(15,921)
Other
Schedule Of Available For Sale Securities [Line Items]
12 months or more, Fair Value	299	497
12 months or more, Unrealized Loss	(1)	(3)
Total, Fair Value	299	497
Total, Unrealized Loss	(1)	(3)
Agency Mortgage-backed Securities
Schedule Of Available For Sale Securities [Line Items]
12 months or more, Fair Value	356,193	387,151
12 months or more, Unrealized Loss	(6,988)	(13,811)
Total, Fair Value	356,193	387,151
Total, Unrealized Loss	(6,988)	(13,811)
Corporate Bonds
Schedule Of Available For Sale Securities [Line Items]
Less than 12 months, Fair Value	3,930	38,706
Less than 12 months, Unrealized Loss	(70)	(294)
Total, Fair Value	3,930	38,706
Total, Unrealized Loss	(70)	(294)
Beneficial interests in FHLMC securitization
Schedule Of Available For Sale Securities [Line Items]
Less than 12 months, Fair Value		429
Less than 12 months, Unrealized Loss		(11)
12 months or more, Fair Value	6,605	7,038
12 months or more, Unrealized Loss	(1,828)	(1,802)
Total, Fair Value	6,605	7,467
Total, Unrealized Loss	$ (1,828)	$ (1,813)