Short-Term and Other Borrowings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Federal funds purchased
Debt Instrument [Line Items]
Amount outstanding at year-end	$ 132,270	$ 629,169	$ 359,338
Interest rate at year-end	1.66%	2.54%	1.45%
Average balance outstanding during the year	$ 502,604	$ 323,140	$ 215,895
Weighted-average interest rate during the year	2.36%	2.02%	1.20%
Maximum outstanding at any month end	$ 905,473	$ 629,169	$ 544,203
Customer repurchase agreements
Debt Instrument [Line Items]
Amount outstanding at year-end	$ 9,496	$ 12,005	$ 5,702
Interest rate at year-end	0.61%	0.09%	0.03%
Average balance outstanding during the year	$ 11,655	$ 9,812	$ 6,590
Weighted-average interest rate during the year	0.51%	0.09%	0.04%
Maximum outstanding at any month end	$ 14,208	$ 13,835	$ 8,727
FHLB borrowings
Debt Instrument [Line Items]
Amount outstanding at year-end	$ 2,400,000	$ 3,900,000	$ 2,800,000
Interest rate at year-end	1.68%	2.56%	1.35%
Average balance outstanding during the year	$ 2,523,836	$ 1,769,452	$ 1,395,753
Weighted-average interest rate during the year	2.31%	2.05%	1.08%
Maximum outstanding at any month end	$ 5,000,000	$ 4,000,000	$ 2,800,000