Borrowings (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Jan. 31, 2022	Dec. 31, 2021
Assets Sold under Agreements to Repurchase [Line Items]
Notes and subordinated debt	$ 1,063,793		$ 566,131
Sterling
Assets Sold under Agreements to Repurchase [Line Items]
Long-term debt		$ 516,881
Subordinated Notes Due 2029 | Subordinated Debt
Assets Sold under Agreements to Repurchase [Line Items]
Notes and subordinated debt	$ 274,000		0
Senior notes, interest rate (as a percent)	4.00%
Subordinated Notes Due 2029 | Subordinated Debt | Sterling
Assets Sold under Agreements to Repurchase [Line Items]
Long-term debt		281,000
Subordinated Notes Due 2029 | Subordinated Debt | SOFR rate
Assets Sold under Agreements to Repurchase [Line Items]
Basis spread on variable interest rate	2.53%
Subordinated Notes Due 2030 | Subordinated Debt
Assets Sold under Agreements to Repurchase [Line Items]
Notes and subordinated debt	$ 225,000		$ 0
Senior notes, interest rate (as a percent)	3.875%
Subordinated Notes Due 2030 | Subordinated Debt | Sterling
Assets Sold under Agreements to Repurchase [Line Items]
Long-term debt		$ 235,900
Subordinated Notes Due 2030 | Subordinated Debt | SOFR rate
Assets Sold under Agreements to Repurchase [Line Items]
Basis spread on variable interest rate	3.69%