Deposits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deposits, by Type [Abstract]
Non-interest bearing demand	$ 5,568,300	$ 4,633,500
Interest bearing:
Demand	4,753,200	4,118,900
Savings	4,981,600	4,405,900
Total	186,700	193,000
Time, other	779,800	865,700
Total interest bearing	10,701,300	9,583,500
Total deposits	16,269,600	14,217,000
Brokered time deposits	0
Time deposits obtained through Certificate of Deposit Account Registry Service (CDARS)	104,500	97,300
Time deposits of $250,000 or more	186,700	193,000
FDIC deposit insurance limit	250,000
Time, $250 and Over
Due within 3 months or less	38,800
Due after 3 months and within 6 months	47,200
Due after 6 months and within 12 months	70,600
Due within 2023	18,100
Due within 2024	4,500
Due within 2025	4,400
Due within 2026 and thereafter	3,100
Total	186,700	193,000
Total Time
Due within 3 months or less	272,700
Due after 3 months and within 6 months	209,700
Due after 6 months and within 12 months	293,700
Due within 2023	100,600
Due within 2024	43,700
Due within 2025	28,700
Due within 2026 and thereafter	17,400
Total	966,500
Interest expense, time deposits, $100,000 or more	$ 900	$ 2,700	$ 4,600