Acquisitions Textual (Details) $ / shares in Units, $ in Thousands, $ in Millions	Feb. 25, 2019 USD ($) $ / shares shares	Feb. 25, 2019 CAD ($)	Mar. 31, 2019 shares	Feb. 25, 2019 CAD ($) shares	Dec. 31, 2018 shares
Finite-Lived Intangible Assets, Remaining Amortization Period	20 years	20 years
Payments to Acquire Businesses, Gross | $	$ 491,487
Preferred Stock, Shares Issued			350,000		350,000
SemCAMS Midstream [Member]
Noncontrolling Interest, Ownership Percentage by Parent	51.00%		51.00%	51.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.00%		49.00%	49.00%
Meritage ULC [Member]
Business Acquisition, Percentage of Voting Interests Acquired	100.00%			100.00%
Payments to Acquire Businesses, Gross	$ 490,800	$ 645.6
Reimbursement of Estimated Capital Expenditures	$ 115,800			$ 152.3
SemCAMS Midstream [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.00%			49.00%
Business Acquisition, Percentage of Voting Interests Acquired	51.00%			51.00%
Business combination, contribution to joint venture by noncontrolling interest owner	$ 597,200			$ 785.6
Contribution to joint venture, potential contingent consideration payable, noncontrolling interest	$ 11,200			$ 14.7
Noncontrolling Interest [Member] | SemCAMS Midstream [Member]
Preferred Stock, Shares Issued	300,000			300,000
Preferred Stock, Value, Issued	$ 228,100			$ 300.0
Preferred stock per share annualized dividend | $ / shares	$ 87.50
Preferred share conversion, percentage of IPO price	92.50%	92.50%
Transaction fee paid to noncontrolling interest	$ 4,600			$ 6.0
Semcams [Member]
Equity contributed to joint venture	100.00%			100.00%
Proceeds from Divestiture of Businesses	$ 490,800	$ 645.6
Reimbursements for deposits paid	23,200	30.6
Contribution to joint venture, potential contingent consideration	11,200	14.7
Contribution to joint venture, contingent consideration, potential special share dividends	38,000	50.0
Deposits made	$ 22,300	$ 29.4