Significant Accounting Policies Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of certain income tax effects related to the change in the U.S. statutory federal income tax rate under the Tax Cuts and Jobs Act to retained earnings			$ 9,535
Cumulative Effect of New Accounting Principle in Period of Adoption					$ (2,285)
Gross interchange and debit card transaction fees	$ 6,475		19,029
Gross cost related to interchange and debit card transactions	2,976	$ 2,980	8,926	$ 9,094
Interchange and debit card transaction fees	$ 3,499	$ 5,884	$ 10,103	$ 17,150