Noninterest Income - Gains and Losses on Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Other Income and Expenses [Abstract]
Gains on exercises, net	$ 30,047	$ 18,287	$ 90,357	$ 42,808
Terminations	(481)	(1,432)	(2,931)	(3,158)
Changes in fair value, net	7,995	17,286	19,787	32,743
Gains on equity warrant assets, net	$ 37,561	$ 34,141	$ 107,213	$ 72,393