Statement of Cash Flows - Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash paid during the year for:
Interest	$ 15,810	$ 15,728
Income taxes	$ 38	(32)
Non-cash investing activities:
Derecognized property and equipment for leases that qualified as operating leases after completion of construction		(15,390)
Property and equipment acquired through third party capital lease arrangements		2,007
Non-cash financing activities:
Derecognized right to use liabilities for leases that qualified as operating leases after completion of construction		(15,393)
Third-party capital lease arrangements to acquire property and equipment		$ 2,007