Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 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	765,842	$ 765,842
CDI current period amortization	(1,835)	(2,193)	(5,611)	(6,713)
Indefinite-lived Intangible Assets (Excluding Goodwill)	919	919	919	919
Other intangible assets, net	21,123	28,745	21,123	28,745		$ 26,734
Total goodwill and intangible assets, end of period	786,965	794,587	786,965	794,587
Core Deposits [Member]
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					$ (83,434)	$ (79,658)	$ (75,454)	$ (70,934)
Core deposit intangible, net, beginning of period	22,039	30,019	25,815	34,539
CDI current period amortization	(1,835)	(2,193)	(5,611)	(6,713)
Total core deposit intangible, end of period	$ 20,204	$ 27,826	$ 20,204	$ 27,826