Income Taxes - Schedule of Deferred Tax Asset and Liability (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets
Net operating losses	$ 352,001	$ 223,402
Alternative minimum tax credits	218,773	228,693
Foreign tax credits	3,816	3,837
Derivative instruments	13,771	0
Incentive compensation	22,852	22,509
Deferred compensation	8,217	7,869
Post-retirement benefits	13,865	13,556
Other	2,743	2,905
Less: valuation allowance	(5,186)	(4,965)
Total	630,852	497,806
Deferred Tax Liabilities
Properties and equipment	1,207,545	1,303,840
Equity method investments	2,754	1,202
Total	1,210,299	1,305,042
Net deferred tax liabilities	$ 579,447	$ 807,236