Fair Value Measurements - Assets measured on a recurring basis (Details) - Fair Value, measurements, recurring - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Interest rate contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year		$ 20,743	$ 3,847	$ 3,088	$ 2,012
Total gains or losses (realized/unrealized):
Included in earnings	[1]	(4,438)	191	13,217	2,026
Purchases, issuances, sales and settlements:
Balance, end of year		16,305	4,038	16,305	4,038
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held		(4,438)	191	13,217	2,026
Other assets - MSRs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year		29,035	41,966	42,022	51,539
Total gains or losses (realized/unrealized):
Included in earnings	[1]	(3,548)	(6,301)	(20,945)	(18,579)
Purchases, issuances, sales and settlements:
Issuances		3,244	1,600	7,654	4,305
Balance, end of year		28,731	37,265	28,731	37,265
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held		(3,548)	(6,301)	(20,945)	(18,579)
Other assets - SBIC investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year		152,784	102,065	119,475	80,074
Total gains or losses (realized/unrealized):
Included in earnings	[1]	7,846	10,239	30,388	24,310
Purchases, issuances, sales and settlements:
Purchases		3,732	7,944	14,499	15,864
Balance, end of year		164,362	120,248	164,362	120,248
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held		$ 7,846	$ 10,239	$ 30,388	$ 24,310

[1] Included in noninterest income in the Unaudited Condensed Consolidated Statements of Income.