Cash and Cash Equivalents (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Abstract]
Cash due from Federal Reserve Bank	$ 1,500,000,000	$ 1,900,000,000
Cash due from depository institutions	43,100,000	26,900,000
Outstanding cash equivalents	0	0
Interest income from term deposit facility	500,000	200,000
Funds on deposit under the Term Deposit Facility program	0	0
Average reserve balances with Federal Reserve	$ 0	$ 500,000