Allowance for Loan Losses - (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016
Allowance For Loan And Lease Losses [Line Items]
Provision (recoupment) for loan losses					$ 5,820	$ 17,076
Impaired loans	$ 24,600				24,600
Energy Loans [Member]
Allowance For Loan And Lease Losses [Line Items]
Specific Reserve in Provision				$ 4,300		15,100
Commercial and Industrial [Member]
Allowance For Loan And Lease Losses [Line Items]
Specific Reserve in Provision		$ 2,100			3,400
Non ASC 310-30 [Member]
Allowance For Loan And Lease Losses [Line Items]
Charge-offs, net	100		$ 3,500		0	4,000
Provision (recoupment) for loan losses	4,103		6,400		5,903	17,881
ASC 310-30 [Member]
Allowance For Loan And Lease Losses [Line Items]
Provision (recoupment) for loan losses	$ (78)		$ 57		$ (83)	$ (805)