Related Party Transactions (Details) - USD ($)			12 Months Ended
	Jan. 02, 2018	May 08, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transactions
Deposits from related parties held by the Company			$ 4,700,000	$ 7,500,000
Total assets			3,393,133,000	2,718,512,000	$ 2,269,442,000
Total deposits			2,943,561,000	$ 2,428,621,000
Key loan processing vendors
Related Party Transactions
Ownership interest as a percentage				30.00%
Fees paid to related party			3,700,000	$ 3,700,000
Amount accrued for services received			253,000	353,000
Law firm
Related Party Transactions
Fees paid to related party			3,000,000	$ 2,100,000	$ 1,900,000
Messrs. Petrie and Rogers | Purchase Agreement | JSB
Related Party Transactions
Purchase price excluding cost of funds		$ 5,400,000
Amount of cost of funds to be paid for each thirty days after June 30, 2017, proprated to the closing date		$ 16,000
Period for which cost of fund to be raised by company		30 days
Percentage of purchase price equal to the price paid by Company’s directors and executive officers, plus expenses and a cost of funds		3.75%
Messrs. Petrie and Rogers | Purchase Agreement | JSB | Subsequent event
Related Party Transactions
Purchase price	$ 5,500,000
JSB
Related Party Transactions
Total assets			43,000,000
Total deposits			$ 36,900,000