Fair Value Measurements - Assets measured on a recurring basis (Details) - Fair Value, measurements, recurring - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Interest rate contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year		$ 3,088	$ 2,012
Total gains or losses (realized/unrealized):
Included in earnings	[1]	9,322	1,146
Purchases, issuances, sales and settlements:
Balance, end of year		12,410	3,158
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held		9,322	1,146
Other assets - MSRs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year		42,022	51,539
Total gains or losses (realized/unrealized):
Included in earnings	[1]	(12,461)	(5,053)
Purchases, issuances, sales and settlements:
Issuances		1,671	1,059
Balance, end of year		31,232	47,545
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held		(12,461)	(5,053)
Other assets - SBIC investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year		119,475	80,074
Total gains or losses (realized/unrealized):
Included in earnings	[1]	27,658	7,557
Purchases, issuances, sales and settlements:
Purchases		9,267	5,712
Balance, end of year		156,400	93,343
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held		$ 27,658	$ 7,557

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