Loans and Allowance for Loan Losses (Narrative) (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2017 USD ($) contract agreement	Jun. 30, 2016 USD ($) contract	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 238,219	$ 238,219		$ 317,970
TDRs both accruing and nonaccruing	186,800	186,800		121,700
Post-Modification outstanding recorded investment		$ 104,336	$ 58,347
Number of TDRs subsequently defaulted | contract		0	0
TDRs and loans impaired with minimum aggregate relationship balances		$ 1,000
Loans receivable	18,473,841	18,473,841	$ 16,035,796	16,752,151
Loans receivable	154,000	154,000
Real estate acquired through foreclosure	17,996	17,996		18,884
Loans held for sale	26,787	26,787		34,064
Short-term borrowings	1,810,907	1,810,907		1,225,406
Write-down for termination of FDIC loss share agreement	6,603	6,603
Settlement amount	3,234	$ 3,234	21,075	16,219	$ 29,868
Performing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period for which payments of principal and interest are past due		less than 90 days
Troubled Debt Restructurings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	96,300	$ 96,300		81,900
Troubled Debt Restructurings [Member] | Loans With Extended Amortization Terms Or Other Payment Concessions [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Extended terms and other payment concessions		28,400	31,000
Troubled Debt Restructurings [Member] | Loans With Significant Covenant Waivers [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Convenant waivers		40,200
Troubled Debt Restructurings [Member] | Loans With Other Modifications [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Post-Modification outstanding recorded investment		$ 35,700
Other Modifications			27,300
FDIC Loss Share Agreement [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loss share agreements | agreement		2
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	14,342	$ 14,342		12,351
Post-Modification outstanding recorded investment		42
Loans receivable	2,093,287	2,093,287	$ 2,064,368	2,059,931
Real estate in process of foreclosure	4,200	4,200		10,100
Real estate acquired through foreclosure	2,700	2,700		3,100
Consumer [Member] | Performing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable	$ 2,078,857	$ 2,078,857		$ 2,046,757