Transactions with Shareholders (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Transactions with Shareholders [Line Items]
Capital Stock Outstanding	$ 2,266,329		$ 1,869,130
Par Value of Advances	44,916,402		34,583,887
Total Accrued Interest Receivable	109,878		112,163
Interest income on advances	168,659	$ 247,877
Fees on letters of credit	3,322	2,964
Citizens Bank, N.A. [Member]
Transactions with Shareholders [Line Items]
Capital Stock Outstanding	$ 342,580		$ 222,684
Percent of Total Capital Stock Outstanding	15.10%		11.90%
Par Value of Advances	$ 8,005,678		$ 5,005,773
Percentage of total par value of advances	17.80%		14.50%
Total Accrued Interest Receivable	$ 1,072		$ 1,678
Percent of Total Accrued Interest Receivable on Advances	2.30%		3.50%
Interest income on advances	$ 23,750	$ 39,113
Percent of total advances interest income	14.10%	15.80%
Fees on letters of credit	$ 1,586	$ 1,878
Percent of total fees on letters of credit	61.80%	81.40%
Directors' Financial Institutions [Member]
Transactions with Shareholders [Line Items]
Capital Stock Outstanding	$ 452,365		$ 112,811
Percent of Total Capital Stock Outstanding	19.90%		6.00%
Par Value of Advances	$ 10,137,669		$ 2,224,141
Percentage of total par value of advances	22.60%		6.40%
Total Accrued Interest Receivable	$ 4,120		$ 3,581
Percent of Total Accrued Interest Receivable on Advances	8.90%		7.40%
Minimum [Member]
Transactions with Shareholders [Line Items]
Definition of shareholder concentration, minimum percent	10.00%