Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets [Roll Forward]
Total goodwill, end of period	$ 765,842	$ 765,842	$ 765,842
Core deposit intangible, net, beginning of period	35,458
CDI current period amortization	(8,724)	(10,479)	(12,236)
Indefinite-lived Intangible Assets (Excluding Goodwill)	919	919	919
Total core deposit intangible, end of period	26,734	35,458
Intangible Assets, Net (Excluding Goodwill)	26,734	35,458	45,937
Total goodwill and intangible assets, end of period	792,576	801,300	811,779
Core Deposits [Member]
Goodwill and Intangible Assets [Roll Forward]
Gross core deposit intangible balance, beginning of period	105,473	105,473	105,473
Accumulated amortization, beginning of period	(70,934)	(60,455)	(48,219)
Core deposit intangible, net, beginning of period	34,539	45,018	57,254
CDI current period amortization	(8,724)	(10,479)	(12,236)
Total core deposit intangible, end of period	$ 25,815	$ 34,539	$ 45,018
Estimated life of CDI, in years	10 years