Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Basis Of Presentation [Line Items]
Cash and cash equivalents	$ 117,300	$ 89,200
Interest earning deposits with banks	2,200	7,100
Federal funds sold	65,900	67,500
Individually impaired non-accrual loans	138,200	170,900
Non-accrual loans	168,370	197,757
Impaired loans, including accruing troubled debt restructuring	301,800	442,148
Accruing troubled debt restructuring	223,900	348,400	$ 556,400
Loans, net of deferred fees and costs	22,177,069	20,836,382
Low Income Housing Tax Credit Partnerships [Member]
Basis Of Presentation [Line Items]
Carrying value of VIE assets and liabilities, net	18,900	10,900
Maximum [Member]
Basis Of Presentation [Line Items]
Retail loans and commercial loans, evaluated for impairment	1,000
Cash And Cash Equivalents [Member]
Basis Of Presentation [Line Items]
Total deposits	$ 100	$ 125
DRR Methodology [Member]
Basis Of Presentation [Line Items]
Calculation for allowance for loan losses on commercial loans as percent of total loan portfolio	35.00%
Loans, net of deferred fees and costs	$ 6,700,000
Loans, net, percent	29.80%