Goodwill and Other Intangible Assets (Goodwill) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($)
Goodwill [Roll Forward]
Balance as of December 31, 2019	$ 497,267
Goodwill acquired and adjustments during the year	0
Balance as of June 30, 2020	497,267
Community Banking Reporting Unit
Goodwill [Roll Forward]
Balance as of December 31, 2019	256,323
Goodwill acquired and adjustments during the year	0
Balance as of June 30, 2020	256,323
Wholesale Banking Reporting Unit
Goodwill [Roll Forward]
Balance as of December 31, 2019	171,636
Goodwill acquired and adjustments during the year	0
Balance as of June 30, 2020	171,636
Consumer Mortgages Reporting Unit
Goodwill [Roll Forward]
Balance as of December 31, 2019	44,877
Goodwill acquired and adjustments during the year	0
Balance as of June 30, 2020	44,877
Wealth Management Reporting Unit
Goodwill [Roll Forward]
Balance as of December 31, 2019	24,431
Goodwill acquired and adjustments during the year	0
Balance as of June 30, 2020	$ 24,431