Unsecured Secured Notes (Details) $ / shares in Units, shares in Thousands, $ in Thousands			3 Months Ended
	Mar. 29, 2017 USD ($)	Dec. 16, 2016 USD ($)	Mar. 31, 2017 USD ($) item $ / shares shares	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Oct. 08, 2014 USD ($)	Jul. 03, 2013 USD ($)	Feb. 15, 2013 USD ($)
Convertible Senior Notes
Principal Amount			$ 2,073,229		$ 2,053,229
Unamortized deferred financing costs			(6,641)		(5,822)
Carrying amount of debt components			2,033,384		2,011,544
Carrying amount of conversion option equity components recorded in additional paid-in capital			$ 31,638		45,988
Closing share price (in dollars per share) | $ / shares			$ 22.58
Loss on extinguishment of debt			$ 5,916
Conversion spread included in computation of diluted EPS (in shares) | shares			3,220
Interest Expense			$ 65,860	$ 56,520
Conversion upon satisfaction of closing market price condition
Convertible Senior Notes
Minimum number of conditions to be satisfied for conversion of debt | item			1
Minimum trading period as a basis for debt conversion			20 days
Consecutive trading period as a basis for debt conversion			30 days
Conversion upon satisfaction of closing market price condition | Minimum
Convertible Senior Notes
Percentage of per share value of distributions that exceeds the market price of the entity's common stock as a basis for debt conversion			10.00%
Conversion upon satisfaction of closing market price condition | Maximum
Convertible Senior Notes
Period of average closing market price of common stock as a basis for debt conversion			10 days
Conversion upon satisfaction of trading price condition
Convertible Senior Notes
Consecutive trading period as a basis for debt conversion			5 days
Conversion upon satisfaction of trading price condition | Maximum
Convertible Senior Notes
Percentage of conversion price and last reported sales price as a basis for debt conversion			98.00%
2017 Notes
Convertible Senior Notes
Amount issued						$ 431,300
Principal Amount			$ 411,885		411,885
Coupon Rate (as a percent)			3.75%			3.75%
Effective Rate (as a percent)			5.86%
Remaining Period of Amortization			6 months
Conversion Rate			41.7397
Conversion price (in dollars per share) | $ / shares			$ 23.96
Amount by which if-converted value of the Notes are less than principal amount			$ 23,700
Conversion spread included in computation of diluted EPS (in shares) | shares			0
2017 Notes | Conversion upon satisfaction of closing market price condition | Minimum
Convertible Senior Notes
Percentage of conversion price as a basis for debt conversion			110.00%
2018 Notes
Convertible Senior Notes
Amount issued								$ 600,000
Principal Amount			$ 369,981		599,981
Coupon Rate (as a percent)			4.55%					4.55%
Effective Rate (as a percent)			6.10%
Remaining Period of Amortization			10 months 24 days
Conversion Rate			47.5317
Conversion price (in dollars per share) | $ / shares			$ 21.04
Conversion Spread Value - Shares | shares			1,200
Amount by which if-converted value of the Notes exceed principal amount			$ 27,100
2019 Notes
Convertible Senior Notes
Amount issued							$ 460,000
Principal Amount			$ 341,363		341,363
Coupon Rate (as a percent)			4.00%				4.00%
Effective Rate (as a percent)			5.35%
Remaining Period of Amortization			1 year 9 months 18 days
Conversion Rate			50.2114
Conversion price (in dollars per share) | $ / shares			$ 19.92
Conversion Spread Value - Shares | shares			2,020
Amount by which if-converted value of the Notes exceed principal amount			$ 45,600
Conversion spread included in computation of diluted EPS (in shares) | shares			3,200
2018 Notes and 2019 Notes | Conversion upon satisfaction of closing market price condition | Minimum
Convertible Senior Notes
Percentage of conversion price as a basis for debt conversion			130.00%
2021 Senior Notes
Convertible Senior Notes
Amount issued		$ 700,000
Principal Amount			$ 700,000		700,000
Coupon Rate (as a percent)		5.00%	5.00%
Effective Rate (as a percent)			5.32%
Remaining Period of Amortization			4 years 8 months 12 days
2021 Senior Notes | Debt instrument redemption period one
Convertible Senior Notes
Percentage of principal amount that may be redeemed		100.00%
2021 Senior Notes | Debt instrument redemption period two
Convertible Senior Notes
Percentage of principal amount that may be redeemed		35.00%
2023 Notes
Convertible Senior Notes
Principal Amount			$ 250,000
Coupon Rate (as a percent)			4.38%
Effective Rate (as a percent)			4.86%
Remaining Period of Amortization			6 years
Conversion Rate			38.5959
Conversion price (in dollars per share) | $ / shares			$ 25.91
Amount by which if-converted value of the Notes are less than principal amount			$ 32,100
Portion of repurchase price attributable to equity component recognized as a reduction of additional paid-in-capital			$ 3,755
Conversion spread included in computation of diluted EPS (in shares) | shares			0
Convertible Senior Notes
Convertible Senior Notes
Unamortized discount			$ (23,907)		(26,135)
Amount by which if-converted value of the Notes exceed principal amount			$ 5,900
Amount of debt repurchased				0
Debt repurchased amount				$ 0
Conversion of principal not included in computation of diluted EPS (in shares | shares			58,400
Convertible Senior Notes | 2018 Notes
Convertible Senior Notes
Coupon Rate (as a percent)	4.55%
Carrying amount of conversion option equity components recorded in additional paid-in capital			$ 18,100
Amount by which if-converted value of the Notes exceed principal amount			27,100
Debt repurchased amount	$ 230,000
Convertible Senior Notes | 2019 Notes
Convertible Senior Notes
Amount by which if-converted value of the Notes exceed principal amount			45,600
Convertible Senior Notes | 2023 Notes
Convertible Senior Notes
Amount issued	250,000
Gross proceeds	$ 247,500
Coupon Rate (as a percent)	4.375%
Carrying amount of debt components	$ 243,700
Carrying amount of conversion option equity components recorded in additional paid-in capital	3,800
Amount of debt repurchased	$ 250,700
Senior Notes
Convertible Senior Notes
Unamortized discount			$ (9,297)		$ (9,728)