Goodwill and Other Intangible Assets (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 790,972,000	$ 745,523,000	$ 621,193,000
Goodwill impairment charges	$ 0	0	$ 0
Estimated amortization expense succeeding period	5 years
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average remaining life	8 years
Other Identifiable Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average remaining life	15 years
FNBC Transactions [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill		$ 124,330,000