Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Allowance for loan losses	$ 20,446	$ 45,763
Acquisition-related fair value adjustments	27,607	54,704
Accrued stock-based compensation	4,082	18,891
Loss and tax credit carry forwards	57,969	76,446
Depreciation	2,954	11,270
Nonaccrual loan interest	6,155	9,465
Accrued expense	9,200	20,858
Other	9,127	15,751
Total deferred tax assets	137,540	253,148
Deferred tax liabilities:
Loan servicing rights	13,446	20,450
Core deposit intangible assets	6,022	11,844
Goodwill	4,076	6,373
Prepaid expenses	7,390	4,873
Other	7,735	2,762
Total deferred tax liabilities	38,669	46,302
Net deferred tax asset before valuation allowance	98,871	206,846
Valuation allowance	(1,150)	(2,239)
Net deferred tax asset	$ 97,721	$ 204,607