Accounting Policies (Details 3) - USD ($)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2015
Revenue Recognition
Oil and gas imbalances	$ 0	$ 0
Restructuring Charges
Restructuring charges	11,742,000
Recent Accounting Standards
Long-term deferred tax assets	9,182,000	33,209,000
Long-term deferred tax liabilities	337,961,000	502,189,000
Current deferred tax assets	32,268,000
Deferred Tax Liabilities, Net, Current	61,683,000
New Accounting Pronouncement | Accounting Standards Update 2015-17
Recent Accounting Standards
Long-term deferred tax assets	41,500,000
Long-term deferred tax liabilities	399,600,000
Current deferred tax assets	0
Deferred Tax Liabilities, Net, Current	0
New Accounting Pronouncement | Accounting Standards Update 2015-03 and 2015-15 | Long-term Debt [Member]
Recent Accounting Standards
Deferred financing costs and other assets	45,900,000	$ 39,300,000
LTIP
Restructuring Charges
Non-cash expense included in restructuring charges	$ 5,000,000