Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Goodwill and Intangible Assets [Roll Forward]
Total goodwill, beginning of period			$ 765,842
Total goodwill, end of period	$ 765,842	$ 765,842	765,842	$ 765,842
CDI current period amortization	(2,193)	(2,632)	(6,713)	(8,029)
Indefinite-lived Intangible Assets (Excluding Goodwill)	919	919	919	919
Other intangible assets, net	28,745	37,908	28,745	37,908		$ 35,458
Total goodwill and intangible assets, end of period	794,587	803,750	$ 794,587	803,750
Core Deposits [Member]
Goodwill and Intangible Assets [Line Items]
Estimated life of CDI, in years			10 years
Goodwill and Intangible Assets [Roll Forward]
Gross core deposit intangible balance, beginning of period					$ 105,473	105,473	$ 105,473	$ 105,473
Accumulated amortization at beginning of period					$ (75,454)	$ (70,934)	$ (65,852)	$ (60,455)
Core deposit intangible, net, beginning of period	30,019	39,621	$ 34,539	45,018
CDI current period amortization	(2,193)	(2,632)	(6,713)	(8,029)
Total core deposit intangible, end of period	$ 27,826	$ 36,989	$ 27,826	$ 36,989