Significant Accounting Policies Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of certain income tax effects related to U.S. statutory federal income tax rate under the Tax Cuts and Jobs Act			$ 9,535
Cumulative Effect of New Accounting Principle in Period of Adoption					$ (2,285)	$ 0
Gross interchange and debit card transaction fees	$ 6,483		12,554
Gross cost related to interchange and debit card transactions	3,037	$ 2,891	5,950	$ 6,114
Interchange and debit card transaction fees	$ 3,446	$ 5,692	$ 6,604	$ 11,266