General - General information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
General
Decrease in other adjustments to reconcile net margin to net cash provided by operating activities	$ (1,685,000)	$ (1,617,000)
Decrease in cash paid for property additions	$ (259,447,000)	(157,332,000)
Adjustments
General
Decrease in other adjustments to reconcile net margin to net cash provided by operating activities		8,065,000
Decrease in cash paid for property additions		$ 8,065,000