Fair Value Measurements (Carrying Value and Fair Value of Financial Instruments) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets:
Investments, Fair Value Disclosure	$ 9,301,948	$ 7,769,949
Non-marketable equity securities	208,614	253,664
Liabilities:
Time Deposits	5,887,903	7,347,247
Federal funds purchased	180,000	100,000
Fair Value, Inputs, Level 1
Assets:
Cash and cash equivalents	369,776	214,673
Fair Value, Inputs, Level 2
Assets:
Non-marketable equity securities	208,614	253,664
Loans held for sale	4,056	39,731
Derivative assets	138,332	43,686
Liabilities:
Time Deposits	5,905,597	7,377,301
Federal funds purchased	180,000	100,000
FHLB and PPPLF borrowings	4,124,405	4,500,969
Notes Payable, Fair Value Disclosure	818,868	473,327
Derivative liabilities	49,482	19,029
Demand, savings and money market deposits	20,709,307	17,047,344
Fair Value, Inputs, Level 3
Assets:
Loans Receivable, Fair Value Disclosure	24,007,794	23,350,684
Carrying Value
Assets:
Cash and cash equivalents	369,776	214,673
Investments, Fair Value Disclosure	9,300,883	7,769,237
Non-marketable equity securities	208,614	253,664
Loans held for sale	3,816	37,926
Loans Receivable, Fair Value Disclosure	23,505,187	23,046,317
Derivative assets	138,332	43,686
Liabilities:
Time Deposits	5,887,903	7,347,247
Federal funds purchased	180,000	100,000
FHLB and PPPLF borrowings	4,118,460	4,480,501
Notes Payable, Fair Value Disclosure	722,592	429,338
Derivative liabilities	49,482	19,029
Demand, savings and money market deposits	$ 20,709,307	$ 17,047,344