Indebtedness (Schedule of Outstanding Debt) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ 3,551
Unamortized debt discount	6,400
Short-term Debt	252,000		$ 0
Long-term Debt	550,588		550,597
Finance lease liabilities	539		737
Total debt	$ 802,588		550,597
Three Point Zero Three Percent Borrowing From Federal Home Loan Bank Due December 16, 2026 [Member]
Debt Instrument [Line Items]
Interest Rate	3.03%
Original Amount	$ 60,000
Unamortized debt issuance costs	0
Unamortized debt discount	0
Long Term Debt Excluding Debt Discount And Debt Issuance Costs	$ 60,000		60,000
One Point Fifty Six Percent Borrowing From Federal Home Loan Bank Due August 16, 2021 [Member]
Debt Instrument [Line Items]
Interest Rate	1.56%
Original Amount	$ 25,000
Unamortized debt issuance costs	0
Unamortized debt discount	0
Long Term Debt Excluding Debt Discount And Debt Issuance Costs	$ 25,000		25,000
One Point Sixty One Percent Borrowing From Federal Home Loan Bank Due July 21, 2021 [Member]
Debt Instrument [Line Items]
Interest Rate	1.61%
Original Amount	$ 25,000
Unamortized debt issuance costs	0
Unamortized debt discount	0
Long Term Debt Excluding Debt Discount And Debt Issuance Costs	$ 25,000		25,000
Six Point Seventy Percent Senior Notes [Member]
Debt Instrument [Line Items]
Interest Rate	6.70%
Original Amount	$ 100,000
Unamortized debt issuance costs	337
Unamortized debt discount	510
Long Term Debt Excluding Debt Discount And Debt Issuance Costs	$ 99,153		99,125
Seven Point Twenty Five Percent Senior Notes [Member]
Debt Instrument [Line Items]
Interest Rate	7.25%
Original Amount	$ 50,000
Unamortized debt issuance costs	175
Unamortized debt discount	88
Long Term Debt Excluding Debt Discount And Debt Issuance Costs	$ 49,737		49,725
Five Point Three Hundred Seventy Five Senior Notes [Member]
Debt Instrument [Line Items]
Interest Rate	5.375%
Original Amount	$ 300,000
Unamortized debt issuance costs	3,039
Unamortized debt discount	5,802
Long Term Debt Excluding Debt Discount And Debt Issuance Costs	291,159		291,010
Long-term Debt
Debt Instrument [Line Items]
Unamortized debt issuance costs	3,551
Unamortized debt discount	6,400
Long-term Debt	$ 550,588		550,597
Zero Point Seventy Eight Percent Borrowing from FHLBNY Due September 14, 2020. [Member]
Debt Instrument [Line Items]
Interest Rate	0.78%
Original Amount	$ 100,000
Unamortized debt issuance costs	0
Unamortized debt discount	0
Short-term Debt	$ 100,000		0
Zero Point Sixty Eight Percent Borrowing from FHLBNY Due September 18, 2020. [Member]
Debt Instrument [Line Items]
Interest Rate	0.68%
Original Amount	$ 85,000
Unamortized debt issuance costs	0
Unamortized debt discount	0
Short-term Debt	$ 85,000		0
Zero Point Fifty Eight Percent Borrowing from FHLBI Due December 14, 2020. [Member]
Debt Instrument [Line Items]
Interest Rate	0.58%
Original Amount	$ 67,000
Unamortized debt issuance costs	0
Unamortized debt discount	0
Short-term Debt	67,000		0
Short-term Debt
Debt Instrument [Line Items]
Unamortized debt issuance costs	0
Unamortized debt discount	0
Short-term Debt	$ 252,000	$ 302,000	$ 0