Intangibles - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense from amortizable intangible assets, other than lease agreements	$ 15,782,000	$ 14,552,000	$ 19,185,000
Amortization of lease agreement intangible assets and liabilities	(203,000)	(232,000)	(331,000)
Impairment of Intangible Assets (Excluding Goodwill)			0
Impairment charge on indefinite-lived intangible asset	0	0
Amortizable intangible lease liabilities	5,447,000	6,011,000
Lease agreements, accumulated amortization	3,508,000	3,618,000
Amortization benefit recognized from the alliance and product supply agreement	$ 0	$ 0	$ 3,997,000