Long-Term Debt (Narrative) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Notes payable aggregate principal amount	$ 396,286
Other long-term debt maturity year	2053
Subordinated Notes [Member] | Subordinated Notes Payable, Maturing June 2060 [Member]
Debt Instrument [Line Items]
Notes payable issuance date	Jun. 09, 2020
Notes payable aggregate principal amount	$ 172,500
Notes payable maturity date	Jun. 15, 2060
Notes payable interest rate	6.25%
Notes payable beginning payment date	Sep. 15, 2020
Notes payable redemption start date	Jun. 15, 2025
Subordinated Notes [Member] | Subordinated Notes Payable, Maturing June 2045 [Member]
Debt Instrument [Line Items]
Notes payable issuance date	Mar. 09, 2015
Notes payable aggregate principal amount	$ 150,000	$ 150,000
Notes payable maturity date	Jun. 15, 2045
Notes payable interest rate	5.95%
Notes payable beginning payment date	2015-06
Notes payable redemption start date	Jun. 15, 2020
Other Long-Term Debt [Member]
Debt Instrument [Line Items]
Notes payable aggregate principal amount	$ 73,786	$ 87,890
Notes payable agreement period	7 years