Long-Term Debt (Details) - USD ($)						3 Months Ended	6 Months Ended	12 Months Ended
	May. 21, 2015	Nov. 17, 2014	May. 20, 2013	Jun. 29, 2012	Nov. 08, 2011	Jun. 30, 2015	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013	Jun. 22, 2015	Jun. 05, 2015	May. 20, 2015
Debt Instrument [Line Items]
Debt Instrument, Face Amount								$ 2,350,000,000	$ 2,200,000,000	[1]
Unamortized Debt Issuance Expense								34,030,000	33,555,000	[1]
Senior Notes, net of unamortized deferred financing costs (note 5)								2,315,970,000	2,166,445,000	[1]
Gains (Losses) on Extinguishment of Debt								(16,578,000)	0		$ 0
Gains (Losses) on Extinguishment of Debt, Non-Cash Portion								4,123,000	0		0
Net proceeds from debt issuance								490,951,000	589,991,000		490,185,000
Interest Costs, Capitalized During Period								25,100,000	16,200,000		$ 11,000,000
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Compliance, Dividends Excluded From Computation								6,500,000
6.625% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount								0	350,000,000	[1]
Unamortized Debt Issuance Expense								0	4,591,000	[1]
Senior Notes, net of unamortized deferred financing costs (note 5)								$ 0	345,409,000	[1]
6.625% Senior Notes Due 2019 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage								6.625%
Price per Note Tendered													$ 1,006.88	$ 1,036.88
Debt Instrument, Face Amount, Individual Note													1,000	1,000
Debt Instrument, Repurchased Face Amount													1,500,000	$ 242,900,000
Percentage of Notes Tendered														69.00%
Debt Instrument, Repurchase Amount													$ 1,600,000	$ 256,200,000
Gains (Losses) on Extinguishment of Debt						$ (16,578,000)
Debt Instrument, Repurchase Premium						12,500,000
Gains (Losses) on Extinguishment of Debt, Non-Cash Portion						$ 4,123,000
6.625% Senior Notes Due 2019 [Member] | From February 15, 2015 to February 14, 2016 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Repurchase Amount												$ 111,500,000
Debt Instrument, Redemption Price, Percentage							103.313%
6.50% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount								$ 350,000,000	350,000,000	[1]
Unamortized Debt Issuance Expense								4,106,000	4,806,000	[1]
Senior Notes, net of unamortized deferred financing costs (note 5)								345,894,000	345,194,000	[1]
6.50% Senior Notes Due 2021 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					$ 350,000,000
Debt Instrument, Interest Rate, Stated Percentage					6.50%
Net proceeds from debt issuance					$ 343,100,000
Deferred Finance Costs, Gross					$ 6,900,000
6.125% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount								600,000,000	600,000,000	[1]
Unamortized Debt Issuance Expense								8,714,000	9,812,000	[1]
Senior Notes, net of unamortized deferred financing costs (note 5)								591,286,000	590,188,000	[1]
6.125% Senior Notes Due 2022 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 600,000,000
Debt Instrument, Interest Rate, Stated Percentage		6.125%
Net proceeds from debt issuance		$ 590,000,000
Deferred Finance Costs, Gross		$ 10,000,000
6.50% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount								400,000,000	400,000,000	[1]
Unamortized Debt Issuance Expense								5,231,000	5,969,000	[1]
Senior Notes, net of unamortized deferred financing costs (note 5)								394,769,000	394,031,000	[1]
6.50% Senior Notes Due 2023 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage				6.50%
Net proceeds from debt issuance				$ 392,100,000
Deferred Finance Costs, Gross				$ 7,900,000
5% Senior Notes Due 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount								500,000,000	500,000,000	[1]
Unamortized Debt Issuance Expense								7,455,000	8,377,000	[1]
Senior Notes, net of unamortized deferred financing costs (note 5)								492,545,000	491,623,000	[1]
5% Senior Notes Due 2024 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 500,000,000
Debt Instrument, Interest Rate, Stated Percentage			5.00%
Net proceeds from debt issuance			$ 490,200,000
Deferred Finance Costs, Gross			$ 9,800,000
5.625% Senior Notes Due 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount								500,000,000	0	[1]
Unamortized Debt Issuance Expense								8,524,000	0	[1]
Senior Notes, net of unamortized deferred financing costs (note 5)								$ 491,476,000	$ 0	[1]
5.625% Senior Notes Due 2025 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 500,000,000
Debt Instrument, Interest Rate, Stated Percentage	5.625%
Net proceeds from debt issuance	$ 491,000,000
Deferred Finance Costs, Gross	$ 9,000,000

[1] Prior period amounts have been reclassified to conform to the current period presentation on the accompanying balance sheets. Please refer to the section Recently Issued Accounting Standards in Note 1 – Summary of Significant Accounting Policies for additional discussion.