Student Loans - Narrative (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019 USD ($) loan	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) loan	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) loan	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest	$ 10,314,000		$ 10,314,000		$ 8,341,000
Allowance for losses	8,452,000	$ 8,425,000	8,452,000	$ 8,425,000	8,395,000	$ 8,417,000	$ 9,116,000	$ 9,267,000
TDRs	6,183,000	7,641,000	6,183,000	7,641,000	7,059,000	$ 6,340,000	$ 9,702,000	$ 11,362,000
Accrued interest receivable, charged against interest income	(9,303,000)	$ (7,778,000)	(18,763,000)	$ (16,103,000)
Student loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	65,935,000		65,935,000		68,221,000
Accrued interest	$ 7,866,000		$ 7,866,000		$ 5,984,000
Number of loans | loan	1,583		1,583		1,674
Allowance for losses	$ 1,944,000		$ 1,944,000		$ 1,520,000
TDRs	0		0		0
Accrued interest receivable, charged against interest income			4,000		26,000
Charge-off of loans			103,000		388,000
Student loan | Not yet entered repayment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest	$ 7,767,000		$ 7,767,000		$ 5,866,000
Student loan | Repayment, Deferment, and Forbearance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans | loan	522		522		595
Student loan | Repayment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	$ 12,783,000		$ 12,783,000		$ 15,526,000
Accrued interest	$ 99,000		$ 99,000		$ 118,000
Number of loans | loan	307		307		366
Student loan | Deferment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	$ 2,887,000		$ 2,887,000		$ 1,945,000
Accrued interest	$ 199,000		$ 199,000		$ 79,000
Number of loans | loan	70		70		48
Student loan | Forbearance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans outstanding	$ 6,298,000		$ 6,298,000		$ 7,336,000
Accrued interest	$ 166,000		$ 166,000		$ 212,000
Number of loans | loan	145		145		181
Student loan | General reserve
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for losses	$ 769,000		$ 769,000		$ 880,000
Student loan | Insolvent loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for losses	$ 1,175,000		$ 1,175,000		$ 640,000