Balance Sheet Offsetting - Financial Instruments Derivative Assets Liabilities and Resell Agreements Net of Amount Not Offset (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	$ 14,543	$ 29,921
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(10,825)	(20,436)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	(2,725)	(6,035)
Net Amount, Derivatives, Financial Assets	993	3,450
Net Amount Recognized, Resell Agreements, Financial Assets	13,442	9,642
Gross Amounts Not Offset, Financial Instruments, Resell Agreements, Financial Assets	0	0
Gross Amounts Not Offset, Collateral, Resell Agreements, Financial Assets	(13,442)	(9,642)
Net Amount, Resell Agreements, Financial Assets	0	0
Net Amount Recognized, Total Financial Assets	27,985	39,563
Gross Amounts Not Offset, Collateral, Financial Assets	(16,167)	(15,677)
Net Amount, Financial Assets	993	3,450
Net Amount Recognized, Derivatives, Financial Liabilities	40,198	47,898
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(10,825)	(20,436)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(28,803)	(26,307)
Net Amount, Derivatives, Financial Liabilities	570	1,155
Net Amount Recognized, Repurchase Agreements, Financial Liabilities	883,947	791,119
Gross Amounts Not Offset, Financial Instruments, Repurchase Agreements, Financial Liabilities	0	0
Gross Amounts Not Offset, Collateral, Repurchase Agreements, Financial Liabilities	(883,947)	(791,119)
Net Amount, Repurchase Agreements, Financial Liabilities	0	0
Net Amount Recognized, Financial Liabilities	924,145	839,017
Gross Amounts Not Offset, Collateral, Financial Liabilities	(912,750)	(817,426)
Net Amount, Financial Liabilities	570	1,155
Counterparty A [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	743	627
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(743)	(627)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	16,092	18,653
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(743)	(627)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(15,347)	(17,626)
Net Amount, Derivatives, Financial Liabilities	2	400
Counterparty B [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	6,901	17,308
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(5,795)	(9,506)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	(413)	(4,925)
Net Amount, Derivatives, Financial Assets	693	2,877
Net Amount Recognized, Derivatives, Financial Liabilities	5,795	9,506
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(5,795)	(9,506)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	0	0
Net Amount, Derivatives, Financial Liabilities	0	0
Counterparty C [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	6,059	7,991
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(3,447)	(7,539)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	(2,312)	0
Net Amount, Derivatives, Financial Assets	300	452
Net Amount Recognized, Derivatives, Financial Liabilities	3,447	7,539
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(3,447)	(7,539)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	0	0
Net Amount, Derivatives, Financial Liabilities	0	0
Other Counterparties [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	840	3,995
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(840)	(2,764)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	(1,110)
Net Amount, Derivatives, Financial Assets	0	121
Net Amount Recognized, Derivatives, Financial Liabilities	14,864	12,200
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(840)	(2,764)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(13,456)	(8,681)
Net Amount, Derivatives, Financial Liabilities	$ 568	$ 755