Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Goodwill and Intangible Assets [Roll Forward]
Total goodwill, beginning of period	$ 765,842
Total goodwill, end of period	765,842	$ 765,842
CDI current period amortization	(1,924)	(2,310)
Indefinite-lived Intangible Assets (Excluding Goodwill)	919	919
Other intangible assets, net	24,810	33,148	$ 26,734
Total goodwill and intangible assets, end of period	790,652	798,990
Core Deposits [Member]
Goodwill and Intangible Assets [Roll Forward]
Gross core deposit intangible balance, beginning of period			105,473	$ 105,473
Accumulated amortization at beginning of period			$ (79,658)	$ (70,934)
Core deposit intangible, net, beginning of period	25,815	34,539
CDI current period amortization	(1,924)	(2,310)
Total core deposit intangible, end of period	$ 23,891	$ 32,229