Loans and Allowance for Loan Losses (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) contract agreement	Mar. 31, 2016 USD ($) contract	Dec. 31, 2016 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 262,649		$ 317,970
TDRs both accruing and nonaccruing	159,900		121,700
Post-Modification outstanding recorded investment	$ 45,092	$ 51,246
Number of TDRs subsequently defaulted | contract	0	0
TDRs and loans impaired with minimum aggregate relationship balances	$ 1,000
Real estate acquired through foreclosure	17,068		18,884
Loans held for sale	20,883		34,064
Short-term borrowings	$ 2,121,932		1,225,406
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	$ 112,600		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	27,400	$ 26,800
Troubled Debt Restructurings [Member] | Loans With Significant Covenant Waivers [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Convenant waivers	10,700
Troubled Debt Restructurings [Member] | Loans With Other Modifications [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Post-Modification outstanding recorded investment	$ 6,900
Other Modifications		24,600
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	$ 13,424		12,351
Real estate in process of foreclosure	7,500		10,100
Real estate acquired through foreclosure	3,100
Consumer [Member] | FDIC Loss Share Agreement [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Real estate in process of foreclosure	3,700		4,900
Real estate acquired through foreclosure	$ 700		$ 900
Non-Single Family Portfolio [Member] | FDIC Loss Share Agreement [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recovery period	3 years
Percentage of recoveries on reimbursed losses due to FDIC	80.00%
Single Family Portfolio [Member] | FDIC Loss Share Agreement [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans covered by loss share agreement	$ 143,800	$ 168,100