Goodwill and Identifiable Intangible Assets - Goodwill by Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Goodwill, beginning of period	$ 379,627	$ 366,156
Goodwill from Reliance merger during 2017		13,471
Adjustment during 2018	0
Balance, end of period	379,627	379,627
General Banking [Member]
Goodwill [Roll Forward]
Goodwill, beginning of period	334,603	321,132
Goodwill from Reliance merger during 2017		13,471
Adjustment during 2018	0
Balance, end of period	334,603	334,603
Insurance [Member]
Goodwill [Roll Forward]
Goodwill, beginning of period	45,024	45,024
Goodwill from Reliance merger during 2017		0
Adjustment during 2018	0
Balance, end of period	$ 45,024	$ 45,024