Securities (Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months Fair Value	$ 76,756	$ 1,157,774
Less than 12 Months Unrealized Losses	(447)	(13,446)
12 Months or More Fair Value	47,270	521,420
12 Months or More Unrealized Losses	(1,044)	(6,994)
Total Fair Value	124,026	1,679,194
Total Unrealized Losses	(1,491)	(20,440)
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months Fair Value	49,116	1,055,903
Less than 12 Months Unrealized Losses	(317)	(12,424)
12 Months or More Fair Value	47,175	491,539
12 Months or More Unrealized Losses	(1,044)	(6,798)
Total Fair Value	96,291	1,547,442
Total Unrealized Losses	(1,361)	(19,222)
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months Fair Value	20,703	89,508
Less than 12 Months Unrealized Losses	(73)	(880)
12 Months or More Fair Value	95	6,799
12 Months or More Unrealized Losses	0	(109)
Total Fair Value	20,798	96,307
Total Unrealized Losses	(73)	(989)
State and Municipal Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months Fair Value	6,937	12,363
Less than 12 Months Unrealized Losses	(57)	(142)
12 Months or More Fair Value	0	12,587
12 Months or More Unrealized Losses	0	(82)
Total Fair Value	6,937	24,950
Total Unrealized Losses	$ (57)	(224)
U.S. Government and Government-Sponsored Enterprise Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months Fair Value		0
Less than 12 Months Unrealized Losses		0
12 Months or More Fair Value		10,495
12 Months or More Unrealized Losses		(5)
Total Fair Value		10,495
Total Unrealized Losses		$ (5)