Loans (Carrying Amounts of Purchased Impaired and Nonimpaired Loans Acquired and Carrying Amount of Loans Covered by Loss Share Agreements (Narrative)) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan and lease losses	$ 61,963				$ 55,686				$ 61,963	$ 55,686
Provision expense	9,681	$ 5,238	$ 4,831	$ 4,263	5,328	$ 5,705	$ 889	$ 3,641	24,013	15,563	$ 11,694
2015 Acquisitions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan and lease losses	57				$ 139				57	139
Provision expense									719	$ 12
2015 Acquisitions | Receivables acquired excluding receivables with deteriorated credit quality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments of loans acquired	3,670,000								3,670,000
Estimated fair value of loans acquired	3,590,000								3,590,000
2015 Acquisitions | Receivables acquired with deteriorated credit quality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments of loans acquired	36,900								36,900
Estimated fair value of loans acquired	$ 21,800								$ 21,800