Noninterest Income - Gains and Losses on Investments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Other Income and Expenses [Abstract]
Total net gains on non-marketable and other equity securities	$ 47,973	$ 36,114	$ 80,631	$ 45,172
Losses on sales of available-for-sale securities, net	(275)	0	(3,905)	0
Gains on investment securities, net	$ 47,698	$ 36,114	$ 76,726	$ 45,172