Long-Term Debt Senior Notes (Details)				3 Months Ended			6 Months Ended
		Jun. 30, 2017 USD ($) $ / shares		Jun. 30, 2017 USD ($) $ / shares		Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) $ / shares		Jun. 30, 2016 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)		Aug. 12, 2016 USD ($)	Mar. 31, 2016 USD ($)
Debt Instrument [Line Items]
Senior Notes, Noncurrent		$ 2,767,030,000		$ 2,767,030,000			$ 2,767,030,000				$ 2,766,719,000
Gain (loss) on extinguishment of debt				0		$ 0	(35,000)		$ 15,722,000
Gains (losses) on extinguishment of debt, noncash portion							(22,000)		15,722,000
Convertible Debt, Noncurrent		$ 134,918,000		$ 134,918,000			$ 134,918,000				130,856,000
Capped Call, Cap Price | $ / shares		$ 60.00		$ 60.00			$ 60.00
6.50% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	[1]	$ 344,611,000		$ 344,611,000			$ 344,611,000
Unamortized Debt Issuance Expense		(3,003,000)	[1]	(3,003,000)	[1]		(3,003,000)	[1]			(3,372,000)	[2]
Senior Notes, Noncurrent		341,608,000	[1]	341,608,000	[1]		341,608,000	[1]			343,583,000	[2]
6.125% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		561,796,000		561,796,000			561,796,000
Unamortized Debt Issuance Expense		(6,390,000)		(6,390,000)			(6,390,000)				(6,979,000)	[2]
Senior Notes, Noncurrent		555,406,000		555,406,000			555,406,000				554,817,000	[2]
6.50% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		394,985,000		394,985,000			394,985,000
Unamortized Debt Issuance Expense		(4,071,000)		(4,071,000)			(4,071,000)				(4,436,000)	[2]
Senior Notes, Noncurrent		390,914,000		390,914,000			390,914,000				390,549,000	[2]
5% Senior Notes Due 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		500,000,000		500,000,000			500,000,000
Unamortized Debt Issuance Expense		(6,072,000)		(6,072,000)			(6,072,000)				(6,533,000)
Senior Notes, Noncurrent		493,928,000		493,928,000			493,928,000				493,467,000
5.625% Senior Notes Due 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		500,000,000		500,000,000			500,000,000
Unamortized Debt Issuance Expense		(7,166,000)		(7,166,000)			(7,166,000)				(7,619,000)
Senior Notes, Noncurrent		492,834,000		492,834,000			492,834,000				492,381,000
6.75% Senior Notes Due 2026 [Domain]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		500,000,000		500,000,000			500,000,000
Unamortized Debt Issuance Expense		(7,660,000)		(7,660,000)			(7,660,000)				(8,078,000)
Senior Notes, Noncurrent		492,340,000		492,340,000			492,340,000				491,922,000
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		2,801,392,000		2,801,392,000			2,801,392,000				2,803,736,000
Unamortized Debt Issuance Expense		(34,362,000)		(34,362,000)			(34,362,000)				(37,017,000)
Senior Notes, Noncurrent		$ 2,767,030,000		$ 2,767,030,000			$ 2,767,030,000				2,766,719,000
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Repurchased Face Amount														$ 46,300,000
Debt Instrument, Repurchased Settlement Amount									29,900,000
Gain (loss) on extinguishment of debt									15,700,000
Debt Instrument, Repurchase Discount									16,400,000
Gains (losses) on extinguishment of debt, noncash portion									$ (700,000)
Senior Notes [Member] | 6.50% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.50%		6.50%			6.50%
Debt Instrument, Face Amount		$ 344,611,000		$ 344,611,000			$ 344,611,000				346,955,000
Debt Instrument, Repurchased Face Amount										$ 2,300,000
Senior Notes [Member] | 6.125% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.125%		6.125%			6.125%
Debt Instrument, Face Amount		$ 561,796,000		$ 561,796,000			$ 561,796,000				561,796,000
Senior Notes [Member] | 6.50% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.50%		6.50%			6.50%
Debt Instrument, Face Amount		$ 394,985,000		$ 394,985,000			$ 394,985,000				394,985,000
Senior Notes [Member] | 5% Senior Notes Due 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.00%		5.00%			5.00%
Debt Instrument, Face Amount		$ 500,000,000		$ 500,000,000			$ 500,000,000				500,000,000
Senior Notes [Member] | 5.625% Senior Notes Due 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.625%		5.625%			5.625%
Debt Instrument, Face Amount		$ 500,000,000		$ 500,000,000			$ 500,000,000				500,000,000
Senior Notes [Member] | 6.75% Senior Notes Due 2026 [Domain]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.75%		6.75%			6.75%
Debt Instrument, Face Amount		$ 500,000,000		$ 500,000,000			$ 500,000,000				500,000,000
Convertible Debt [Member] | 1.50% Senior Convertible Notes Due 2021 [Domain]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		1.50%		1.50%			1.50%
Debt Instrument, Face Amount		$ 172,500,000		$ 172,500,000			$ 172,500,000				172,500,000
Unamortized Debt Issuance Expense		(3,669,000)		(3,669,000)			$ (3,669,000)				(4,131,000)
Debt Instrument, Convertible, Conversion Ratio							24.6914
Debt Instrument, Principal Amount of Note		$ 1,000		$ 1,000			$ 1,000
Debt Instrument, Convertible, Conversion Price | $ / shares		$ 40.50		$ 40.50			$ 40.50
Debt Instrument, Convertible, Initial Fair Value of Liability Component													$ 132,300,000
Debt Instrument, Convertible, Comparable Yield		7.25%
Debt Instrument, Convertible, Initial Value of Equity Component													$ 40,200,000
Interest Expense, Debt				$ 2,500,000			$ 4,900,000
Debt Instrument, Unamortized Discount		$ (33,913,000)		(33,913,000)			(33,913,000)				(37,513,000)
Convertible Debt, Noncurrent		$ 134,918,000		$ 134,918,000			$ 134,918,000				$ 130,856,000

[1] During the first quarter of 2017, the Company repurchased a total of $2.3 million in aggregate principal amount of 6.50% Senior Notes due 2021 in open market transactions at a slight premium. The Company canceled all of these repurchased Senior Notes upon cash settlement.

[2] During the first quarter of 2016, the Company repurchased a total of $46.3 million in aggregate principal amount of certain of its Senior Notes in open market transactions for a settlement amount of $29.9 million, excluding interest. The Company recorded a net gain on extinguishment of debt of approximately $15.7 million for the six months ended June 30, 2016. This amount includes a gain of approximately $16.4 million associated with the discount realized upon repurchase, which was partially offset by approximately $0.7 million related to the acceleration of unamortized deferred financing costs. The Company canceled all of these repurchased Senior Notes upon cash settlement.