Variable Interest Entity - Summary of Carrying Amounts of Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Noncontrolling Interest [Line Items]
Cash and cash equivalents	$ 89,118	$ 121,749	$ 143,548	$ 70,049
Other current assets	45,993	37,658
Property, plant, and equipment, net	942,834	906,722
Intangible assets	416,747	439,198
Other long-term assets	23,334	22,594
Total assets	2,992,606	2,906,645
Current portion of long-term debt	33,553	41,825
Current liabilities	357,880	336,973
Long-term debt	1,667,074	1,697,700
Total liabilities	2,408,238	2,416,408
KFPC
Noncontrolling Interest [Line Items]
Cash and cash equivalents	9,811	14,150
Other current assets	21,899	13,385
Property, plant, and equipment, net	171,796	167,579
Intangible assets	9,529	9,403
Other long-term assets	10,954	2,495
Total assets	223,989	207,012
Current portion of long-term debt	32,545	11,585
Current liabilities	19,597	26,743
Long-term debt	113,691	104,012
Total liabilities	$ 165,833	$ 142,340