Fair Value Measurements - Assets measured on a recurring basis (Details) - Fair Value, measurements, recurring - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Interest rate contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year		$ 12,410	$ 3,158	$ 3,088	$ 2,012
Total gains or losses (realized/unrealized):
Included in earnings	[1]	8,333	689	17,655	1,835
Purchases, issuances, sales and settlements:
Balance, end of year		20,743	3,847	20,743	3,847
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held		8,333	689	17,655	1,835
Other assets - MSRs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year		31,232	47,545	42,022	51,539
Total gains or losses (realized/unrealized):
Included in earnings	[1]	(4,936)	(7,225)	(17,397)	(12,278)
Purchases, issuances, sales and settlements:
Issuances		2,739	1,646	4,410	2,705
Balance, end of year		29,035	41,966	29,035	41,966
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held		(4,936)	(7,225)	(17,397)	(12,278)
Other assets - SBIC investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year		156,400	93,343	119,475	80,074
Total gains or losses (realized/unrealized):
Included in earnings	[1]	(5,116)	6,514	10,767	14,071
Purchases, issuances, sales and settlements:
Purchases		1,500	2,208	22,542	7,920
Balance, end of year		152,784	102,065	152,784	102,065
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held		$ (5,116)	$ 6,514	$ 10,767	$ 14,071

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