Stockholders' Equity and EPS - Reclassification out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gains on investment securities, net	$ 46,055	$ 29,028
Related tax benefit	(49,357)	(107,435)
Net interest income	524,137	512,886
Total reclassification adjustment for (gains) losses included in net income, net of tax	132,253	288,732
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	(45,722)	2,622
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	(61,165)	3,630
Related tax benefit	16,953	(1,010)
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	579	(1)
Net interest income	$ (2,089)	$ 3