Borrowings (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2017	Mar. 31, 2017	Mar. 31, 2016	Sep. 30, 2003
Debt Instrument [Line Items]
Extinguished and Matured Debt	$ 80,000				$ 232,000	$ 268,000
Total Of Debt Matured and ExtinguishedUnder Repurchased Agreement	172,500					$ 500,000
Other borrowings	153	$ 61
Subordinated Debt	$ 36,083	$ 36,083
Trust redeemable preferred securities issued							$ 35,000
Debt Instrument Interest Rate Terms	3-month LIBOR plus 295 basis points
Debt Instrument Basis Spread On Variable Rate	4.55%	3.94%
Gains Losses On Extinguishment Of Debt	$ (80)	$ (12,000)	$ 0
Repayments Of Subordinated Debt	67,000
Due Date 6 2019 Member [Member]
Debt Instrument [Line Items]
Extinguished and Matured Debt				$ 25,000
Due Date 12 2019 Member [Member]
Debt Instrument [Line Items]
Extinguished and Matured Debt				$ 75,000
Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Loans pledged as collateral to secure FHLB advances	1,300,000	1,400,000
Additional Borrowing Capacity	$ 920,000	$ 1,200,000
Weighted average period remaining maturity of FHLB advances	3.2 months	10.6 months
Interest Payable	$ 322
Minimum amount of qualifying collateral	110.00%
Repurchase agreement
Debt Instrument [Line Items]
Interest Payable	$ 369	$ 1,500