Debt and Other Long-Term Liabilities (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended			0 Months Ended				3 Months Ended		6 Months Ended							3 Months Ended					3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Quantity	Jun. 30, 2013	Dec. 31, 2013	Mar. 12, 2013 Senior Notes Original Notes [Member]	Jun. 09, 2014 Senior Notes Senior Unsecured Notes due 2021	Jun. 30, 2014 Senior Notes Senior Unsecured Notes due 2021	Dec. 31, 2013 Senior Notes Senior Unsecured Notes due 2021	Jun. 30, 2014 Credit Facility Federal Funds Effective Swap Rate [Member]	Jun. 30, 2014 Credit Facility London Interbank Offered Rate (LIBOR) [Member]	Jun. 30, 2014 Convertible Notes	Dec. 31, 2013 Convertible Notes	Jun. 30, 2014 Period, June 15, 2017 To June 14, 2018 [Member] Senior Notes Senior Unsecured Notes due 2021	Jun. 30, 2014 Period, June 9, 2014 To June 14, 2017 [Member] Senior Notes Senior Unsecured Notes due 2021	Jun. 30, 2014 Period, June 15, 2018 To June 14, 2019 [Member] Senior Notes Senior Unsecured Notes due 2021	Jun. 30, 2014 Period, June 15, 2019 To June 14, 2020 [Member] Senior Notes Senior Unsecured Notes due 2021	Jun. 30, 2014 Period, June 15, 2020 To June 15, 2021 [Member] Senior Notes Senior Unsecured Notes due 2021	Jun. 30, 2014 Revolving Line of Credit Credit Facility	Dec. 31, 2013 Revolving Line of Credit Credit Facility	Jun. 30, 2014 Term Loans	Jun. 30, 2014 Term Loans Credit Facility	Dec. 31, 2013 Term Loans Credit Facility	Jun. 30, 2014 Common Stock [Member]	Jun. 30, 2014 Common Stock [Member]	Jun. 30, 2014 Scenario One [Member] Period, June 9, 2014 To June 14, 2017 [Member] Senior Notes Senior Unsecured Notes due 2021	Jun. 30, 2014 Scenario Two [Member] Period, June 9, 2014 To June 14, 2017 [Member] Senior Notes Senior Unsecured Notes due 2021
Debt Instrument [Line Items]
Principal amount of debt						$ 350,000,000	$ 300,000,000.0	$ 300,000,000.0
Interest rate, per year						6.00%	5.875%					4.00%
Proceeds from issuance of debt	295,500,000	0	295,500,000	343,769,000		343,800,000	294,000,000
Redemption rate														104.406%		102.938%	101.469%	100.00%								100.00%	105.875%
Maximum aggregate principal amount of notes redeemable															35.00%
Minimum aggregate principal amount of Notes outstanding after redemption															65.00%
Percentage of principal amount of notes required to be offered to purchase the Notes upon a change in control								101.00%
Percentage of principal amount of notes required to be offered to purchase the Notes if certain asset sales are made								100.00%
Minimum percentage of aggregate principal amount of Notes required to declare the principal amount plus accrued and unpaid interest on the Notes to be immediately due and payable in event of default								25.00%
Additional interest payable, per annum, following a registration default, percentage								0.25%
Maximum additional interest payable, per annum, following a registration default, percentage								1.00%
Loss on extinguishment of debt	1,963,000	4,011,000	1,963,000	5,949,000								200,000							1,700,000
Line of credit facility, maximum borrowing capacity																			600,000,000.0			150,000,000.0
Sublimit for issuance of letters of credit																			75,000,000.0
Sublimit for swingline loans																			50,000,000.0
Sublimit for loans in certain foreign countries																			75,000,000.0
Line of credit facility, option to increase borrowing capacity																			200,000,000.0
Basis spread on variable interest rate										0.50%	1.00%
Stated interest rate, minimum										0.25%	1.25%
Stated interest rate, maximum										1.00%	2.00%
Interest rate on amounts outstanding under the credit facility																					2.17%
Debt outstanding	998,424,000		998,424,000		745,523,000			300,000,000	0			33,424,000	51,148,000						165,000,000	0		150,000,000	344,375,000
Effective interest rate at date of issuance												8.50%
Number of notes retired			17,724
Retirement of debt	17,700,000		17,700,000
Conversion of debt, cash	$ 17,720,000	$ 107,179,000	$ 17,724,000	$ 169,634,000
Conversion of debt, issuance of common stock (shares)																								182,777	182,816