Debt (Details)		1 Months Ended	3 Months Ended	6 Months Ended
	Sep. 29, 2015 USD ($)	Jan. 31, 2017 USD ($) $ / shares	Jun. 30, 2017 USD ($) $ / shares	Jun. 30, 2017 USD ($) $ / shares	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Long-term debt
Other			$ 124,000	$ 124,000		$ 297,000
Long-term Debt			3,771,935,000	3,771,935,000		3,604,681,000
Less: current portion			124,000	124,000		297,000
Less: deferred financing costs			31,563,000	31,563,000		26,049,000
Long-term Debt, Excluding Current Maturities, Total			3,740,248,000	3,740,248,000		3,578,335,000
Reduction in long-term debt				377,983,000	$ 148,045,000
Senior Notes.
Long-term debt
Reduction in long-term debt				382,500,000
Payment of debt accrued interest			5,600,000	5,600,000
Consolidated affiliate | Senior Notes.
Long-term debt
Principal amount redeemed			363,200,000	363,200,000
6.15% senior notes due February 2018
Long-term debt
Senior Notes			$ 465,083,000	$ 465,083,000		827,539,000
Interest rate on senior notes due (as a percent)			6.15%	6.15%
9.25% senior notes due January 2019
Long-term debt
Senior Notes			$ 303,489,000	$ 303,489,000		303,489,000
Interest rate on senior notes due (as a percent)			9.25%	9.25%
5.00% senior notes due September 2020
Long-term debt
Senior Notes			$ 669,693,000	$ 669,693,000		669,540,000
Interest rate on senior notes due (as a percent)			5.00%	5.00%
4.625% senior notes due September 2021
Long-term debt
Senior Notes			$ 694,988,000	$ 694,988,000		694,868,000
Interest rate on senior notes due (as a percent)			4.625%	4.625%
5.50% senior notes due January 2023
Long-term debt
Senior Notes			$ 600,000,000	$ 600,000,000		600,000,000
Interest rate on senior notes due (as a percent)			5.50%	5.50%
5.10% senior notes due September 2023
Long-term debt
Senior Notes			$ 346,512,000	$ 346,512,000		346,448,000
Interest rate on senior notes due (as a percent)			5.10%	5.10%
0.75% senior exchangeable notes due January 2024
Long-term debt
Senior Notes			$ 420,061,000	$ 420,061,000
Less: deferred financing costs		$ 9,600,000
Interest rate on senior notes due (as a percent)			0.75%	0.75%
Aggregate amount of senior notes		575,000,000	$ 575,000,000	$ 575,000,000
Debt exchangeable notes				$ 411,200,000
Equity component					$ 163,800,000
Equity issuance costs		$ 3,900,000
Exchange rate of common shares		39.75
Principal amount of notes		$ 1,000,000
Exchange price per common share (in dollars per share) | $ / shares		$ 25.16
Share price of shares purchased (in dollars per share) | $ / shares		$ 17.97
Premium over share price (as a percent)				75.00%
Prepayment of loan upon closing the merger		$ 162,500,000
0.75% senior exchangeable notes due January 2024 | Minimum
Long-term debt
Share issued price (in dollars per share) | $ / shares			$ 25.16	$ 25.16
0.75% senior exchangeable notes due January 2024 | Maximum
Long-term debt
Exchange price per common share (in dollars per share) | $ / shares			$ 31.45	$ 31.45
Term Loan Facility
Long-term debt
Senior Notes						$ 162,500,000
Five-year term loan facility
Long-term debt
Maximum borrowing capacity	$ 325,000,000
Unsecured debt maturity period	5 years
Prepayment of loan upon closing the merger	$ 162,500,000
Revolving Credit Facility
Long-term debt
Revolving credit facility			$ 100,000,000	$ 100,000,000
Amount outstanding			$ 100,000,000	$ 100,000,000
Weighted average interest rate (as a percent)			2.52%	2.52%
Maximum borrowing capacity			$ 2,250,000,000	$ 2,250,000,000
Debt to capital ratio			0.60	0.60
Commercial paper
Long-term debt
Long-term Debt			$ 171,985,000	$ 171,985,000
Amount outstanding			$ 172,000,000	$ 172,000,000
Weighted average interest rate (as a percent)			1.63%	1.63%
Commercial paper | Minimum
Long-term debt
Remaining period to maturity			1 year