Loans and Allowance for Loan Losses (Narrative) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($) contract agreement	Jun. 30, 2015 USD ($) contract	Dec. 31, 2015 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 265,722		$ 159,713
TDRs both accruing and nonaccruing	$ 70,800		13,100
Number of TDRs subsequently defaulted | contract	0	0
TDRs and loans impaired with minimum aggregate relationship balances	$ 1,000
Total loans	16,035,796	$ 14,344,752	15,703,314
Real estate acquired through foreclosure	$ 22,641		26,256
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	$ 34,800		8,800
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	$ 8,541		9,061
Total loans	2,064,368	$ 1,869,451	2,093,465
Real estate in process of foreclosure	7,100		7,400
Real estate acquired through foreclosure	5,900		9,300
Consumer [Member] | Performing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	2,055,003		2,082,238
Consumer [Member] | FDIC Loss Share Agreement [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Real estate in process of foreclosure	3,600		4,100
Real estate acquired through foreclosure	$ 700		1,600
Non-Single Family [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 [Member] | FDIC Loss Share Agreement [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 160,000		$ 170,100