Senior Notes, Convertible Notes and Trust Preferred Securities - Narrative (Details) - 6.804% Trust Preferred Securities - USD ($)	12 Months Ended
	Dec. 31, 2007	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Face amount	$ 200,000,000
Debt interest rate percentage	6.804%
Effective interest percentage		3.636%
Principal amount outstanding on Trust Preferred Securities		$ 129,120,000	$ 129,120,000
Debt issuance costs, gross		$ 1,724,000	$ 1,824,000
London Interbank Offered Rate (LIBOR)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Basis spread on variable rate	1.70%