Derivatives and Hedging Activities (Offsetting Assets) (Details) - USD ($) $ in Thousands		Sep. 30, 2020	Dec. 31, 2019
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset		$ 7,403	$ 16,172
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	[1],[2]	153,534	124,050
Derivative Asset, Net Fair Value Amount, After Offsetting Adjustment		160,937	140,222
Derivative Asset, Not Subject to Master Netting Arrangement	[3]	49	29
Derivative assets		160,986	140,251
Derivative Asset, Fair Value, Amount Offset Against Collateral		160,986	140,251
Over the Counter [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset		4,306	8,743
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		(3,793)	(7,631)
Derivative Asset, Net Fair Value Amount, After Offsetting Adjustment		513	1,112
Derivative Asset, Not Subject to Master Netting Arrangement		49	29
Derivative assets		562	1,141
Derivative Asset, Fair Value, Amount Offset Against Collateral		562	1,141
Exchange Cleared [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset		3,097	7,429
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset		157,327	131,681
Derivative Asset, Net Fair Value Amount, After Offsetting Adjustment		160,424	139,110
Derivative Asset, Not Subject to Master Netting Arrangement		0	0
Derivative assets		160,424	139,110
Derivative Asset, Fair Value, Amount Offset Against Collateral		$ 160,424	$ 139,110

[1] Amounts represent the application of the netting requirements that allow the Bank to settle positive and negative positions, cash collateral and related accrued interest held or placed with the same clearing agent and/or counterparties. Cash collateral posted and related accrued interest was $160.0 million and $138.1 million at September 30, 2020 and December 31, 2019, respectively. Cash collateral received was $2.9 million for September 30, 2020 and $8.2 million for December 31, 2019.

[2] Amounts represent the application of the netting requirements that allow the Bank to settle positive and negative positions and also cash collateral held and related interest accrued or placed by the Bank with the same clearing agent and/or counterparties.

[3] Represents derivatives that are not subject to an enforceable netting agreement (e.g., mortgage delivery commitments).