Interest Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Banking and Thrift, Interest [Abstract]
Interest on unpaid principal balance	$ 440,753	$ 382,983	$ 300,713
Amortization of net deferred origination costs	(57,414)	(48,540)	(36,040)
Interest income on loans, net	383,339	334,443	264,673
Interest on deposits	240	132	171
Total interest income	$ 383,579	$ 334,575	$ 264,844