Parent Company Only Financial Information, Statement of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income
Interest income on notes receivable from subsidiaries	$ 998,099	$ 976,990	$ 749,000
Total income	1,216,498	1,235,148	1,073,900
Expense
Income before income tax expense	406,509	413,349	338,767
Income tax expense	79,720	79,786	109,503
Net income	326,790	333,562	229,264
Preferred stock dividends	15,202	10,784	9,347
Net income available to common equity	311,587	322,779	219,917
Parent Company Only
Income
Income from subsidiaries	341,789	354,637	253,485
Interest income on notes receivable from subsidiaries	13,983	12,199	4,175
Other income	761	994	1,763
Total income	356,532	367,830	259,423
Expense
Interest expense on short and long-term funding	16,802	18,355	18,464
Other expense	6,583	11,736	6,927
Total expense	23,384	30,091	25,391
Income before income tax expense	333,148	337,739	234,032
Income tax expense	6,359	4,176	4,768
Net income	326,790	333,562	229,264
Preferred stock dividends	15,202	10,784	9,347
Net income available to common equity	$ 311,587	$ 322,779	$ 219,917