Loans and Allowance for Credit Losses Allowance for Credit Losses (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Receivables [Abstract]
Allowance for loan and lease losses	$ 166,135	$ 170,233	$ 160,537	$ 157,810	$ 156,050	$ 169,910
Reserve for unfunded lending commitments	6,662		8,873
Allowance for credit losses	$ 172,797	$ 176,941	$ 169,410	$ 167,826	$ 169,247	$ 176,084

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Name:	us-gaap_LoansAndLeasesReceivableAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant