Commitments and Contingencies - Leases and Unconditional Purchase Obligations (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) bbl	Mar. 31, 2015 USD ($)
Operating Leases
Nine Months Ending December 31, 2016	$ 5.9
2017	5.5
2018	3.8
2019	2.1
2020	1.5
Thereafter	2.5
Operating leases	21.3
Unconditional Purchase Obligations
Nine Months Ending December 31, 2016	140.5
2017	130.6
2018	125.4
2019	124.6
2020	108.9
Thereafter	738.1
Unconditional purchase obligations	1,368.1
Unrecorded purchase agreements
Lease expenses	2.2	$ 2.2
Expenses related to long-term commitments	33.2	$ 27.1
Petroleum transportation service agreement with TransCanada | CRRM
Unrecorded purchase agreements
Amount payable related to petroleum transportation service agreements	$ 784.1
Term of agreement	15 years
Minimum quantity of crude oil to be received per day (in barrels) | bbl	25,000
Period over which minimum quantity of crude oil is receivable	20 years