Long-Term Debt - Schedule of Interest Expense Related To Debt (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Debt Disclosure [Abstract]
Interest expense	$ 10,248,000	$ 9,023,000
Amortization of debt issuance costs related to long-term debt, including our credit facility	831,000	842,000
Commitment fees	617,000	788,000
Interest costs capitalized	$ 0	$ 0
Unused capacity, commitment fee percentage	0.30%