Financial Instruments (Details 6) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of long-term debt		$ 682,900		$ 834,600
Carrying value of long-term debt		673,410		880,835
Unit adjustment liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Issuances		(19,145)		0
Gain (Loss) on Sale of Equity Investments		(65,461)		0
Balance at beginning of year		79,934		93,762
Payments		0		(22,320)
Change in fair value to the unit adjustment liability		4,672		8,491
Balance at end of year		0	[1]	79,934
Contingent Consideration for Acquisition [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of year	[1]	$ 79,934
Balance at end of year	[1]			$ 79,934

[1] Does not total due to rounding.