Investment Securities Available for Sale (Schedule of Gross Unrealized Losses on Investment Securities and Fair Value) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	$ 285,770	$ 891,914
Less than 12 Months, Gross Unrealized Losses	(13,847)	(2,468)
12 Months or Longer, Fair Value	32	5,309
12 Months or Longer, Gross Unrealized Losses	(1)	(38)
Total, Fair Value	285,802	897,223
Total, Gross Unrealized Losses	(13,848)	(2,506)
U.S. Government agency securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	38,502
Less than 12 Months, Gross Unrealized Losses	(37)
12 Months or Longer, Fair Value	0
12 Months or Longer, Gross Unrealized Losses	0
Total, Fair Value	38,502
Total, Gross Unrealized Losses	(37)
Mortgage-backed securities issued by U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	6	19,543
Less than 12 Months, Gross Unrealized Losses	(1)	(70)
12 Months or Longer, Fair Value	0	355
12 Months or Longer, Gross Unrealized Losses	0	(2)
Total, Fair Value	6	19,898
Total, Gross Unrealized Losses	(1)	(72)
Mortgage-backed securities issued by U.S. Government sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value		768,040
Less than 12 Months, Gross Unrealized Losses		(2,076)
12 Months or Longer, Fair Value		0
12 Months or Longer, Gross Unrealized Losses		0
Total, Fair Value		768,040
Total, Gross Unrealized Losses		(2,076)
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	320	57,670
Less than 12 Months, Gross Unrealized Losses	(1)	(204)
12 Months or Longer, Fair Value	32	0
12 Months or Longer, Gross Unrealized Losses	(1)	0
Total, Fair Value	352	57,670
Total, Gross Unrealized Losses	(2)	(204)
State and municipal securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	503
Less than 12 Months, Gross Unrealized Losses	(4)
12 Months or Longer, Fair Value	0
12 Months or Longer, Gross Unrealized Losses	0
Total, Fair Value	503
Total, Gross Unrealized Losses	(4)
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	140,993	37,156
Less than 12 Months, Gross Unrealized Losses	(9,129)	(116)
12 Months or Longer, Fair Value	0	4,954
12 Months or Longer, Gross Unrealized Losses	0	(36)
Total, Fair Value	140,993	42,110
Total, Gross Unrealized Losses	(9,129)	(152)
Corporate debt securities and other debt securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	105,446	9,505
Less than 12 Months, Gross Unrealized Losses	(4,675)	(2)
12 Months or Longer, Fair Value	0	0
12 Months or Longer, Gross Unrealized Losses	0	0
Total, Fair Value	105,446	9,505
Total, Gross Unrealized Losses	$ (4,675)	$ (2)