Consolidation and Nature of Operations (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash paid during the period for:
Income taxes, net of refunds	$ 2,503	$ 1,834
Interest, net of amounts capitalized	89,109	84,008
Significant non-cash investing and financing activities:
Accrued capital expenditures	55,286	38,985
Dividends accrued but not yet paid	$ 69,484	$ 65,933