Supplemental Disclosures of Cash Flow Information and Noncash Activities (Supplemental Cash Flow Information) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract]
Cash paid for income taxes, net of refunds received	$ 1,517	$ 2,571	$ 4,189	$ 8,995
Cash paid for interest	$ 7,234	$ 8,503	$ 109,644	$ 111,116