Balance Sheet Offsetting (Assets and liabilities subject to MNA, or repurchase agreements) (Details 2) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Liabilities:
Repurchase Agreements, Gross Amounts of Recognized Liabilities	$ 604,299	$ 504,296
Repurchase Agreements, Gross Amounts Offset in the Statements of Condition	0	0
Repurchase Agreements, Net Amounts of Liabilities Presented in the Statements of Condition	604,299	504,296
Repurchase Agreements, Fair Value of Collateral Pledged	604,299	504,296
Securities Sold under Agreements to Repurchase, Net Amount Offset Against Collateral	0	0
Interest Rate Swap Agreements
Offsetting Assets and Liabilities [Line items]
Net liability positions, aggregate fair value	8,200	300
Institutional Counterparties | Interest Rate Swap Agreements
Assets:
Gross Amounts of Recognized Assets	92	7,572
Gross Amounts Offset in the Statements of Condition	0	0
Net Amounts of Assets Presented in the Statements of Condition	92	7,572
Netting Adjustments per Master Netting Arrangements	92	1,490
Gross Amounts Not Offset in the Statements of Condition - FV of collateral pledged	0	0
Derivative Assets, Net Amount	0	6,082
Liabilities:
Gross Amounts of Recognized Liabilities	8,258	1,490
Gross Amounts Offset in the Statements of Condition	0	0
Net Amounts of Liabilities Presented in the Statements of Condition	8,258	1,490
Derivative Liability, Netting Adjustments per Master Netting Arrangements	92	1,490
Derivative, Collateral, Right to Reclaim Securities	6,113	0
Derivative Liabilities, Net Amount	2,053	0
Private Institutions
Offsetting Assets and Liabilities [Line items]
Securities Sold under Agreements to Repurchase, Fair Value of Collateral	644,300	526,700
Liabilities:
Repurchase Agreements, Gross Amounts of Recognized Liabilities	600,000	500,000
Repurchase Agreements, Gross Amounts Offset in the Statements of Condition	0	0
Repurchase Agreements, Net Amounts of Liabilities Presented in the Statements of Condition	600,000	500,000
Repurchase Agreements, Fair Value of Collateral Pledged	600,000	500,000
Securities Sold under Agreements to Repurchase, Net Amount Offset Against Collateral	0	0
Government Entities
Offsetting Assets and Liabilities [Line items]
Securities Sold under Agreements to Repurchase, Fair Value of Collateral	5,800	6,800
Liabilities:
Repurchase Agreements, Gross Amounts of Recognized Liabilities	4,299	4,296
Repurchase Agreements, Gross Amounts Offset in the Statements of Condition	0	0
Repurchase Agreements, Net Amounts of Liabilities Presented in the Statements of Condition	4,299	4,296
Repurchase Agreements, Fair Value of Collateral Pledged	4,299	4,296
Securities Sold under Agreements to Repurchase, Net Amount Offset Against Collateral	$ 0	$ 0