Stockholders' Equity and EPS - Reclassification out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains on investment securities, net	$ 34,868	$ 47,698	$ 80,923	$ 76,726
Related tax benefit	(87,869)	(119,114)	(137,226)	(226,549)
Net interest income (loss)	512,927	529,403	1,037,064	1,042,289
Total reclassification adjustment for (gains) losses included in net income, net of tax	228,935	317,987	361,188	606,719
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassification adjustment for (gains) losses included in net income, net of tax	(11,443)	565	(57,165)	3,187
Accumulated Net Investment Gain (Loss) Attributable to Parent | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains on investment securities, net	0	275	(61,165)	3,905
Related tax benefit	0	77	16,953	(1,087)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Related tax benefit	(4,388)	141	4,967	(142)
Net interest income (loss)	$ (15,831)	$ 508	$ (17,920)	$ 511