Investment in and Advances to Unconsolidated Affiliates Affiliate Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2012
Investments in and Advances to Affiliates, Affiliate Balance Sheet [Abstract]
Current assets	$ 15.0	$ 24.5
Property and equipment, net	112.1	119.7
Other assets, net	107.3	106.6
Total assets	234.4	250.8
Current liabilities	11.3	21.6
Current portion of long-term debt	8.3	8.3
Long-term debt, excluding current portion	15.7	20.5	$ 50.0
Other liabilities	0.1	0.1
Members' equity	199.0	200.3
Total liabilities and members' equity	$ 234.4	$ 250.8