Long-Term Debt (Narrative) (Details) $ in Thousands		3 Months Ended	6 Months Ended	12 Months Ended
	May. 15, 2014 USD ($) shares	Mar. 31, 2014 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) pricing_tranch	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	May. 14, 2014 USD ($)
Debt Instrument [Line Items]
Long-term Debt				$ 211,558
Proceeds from Dividends Received				0	$ 122,384	$ 0
Amortization of debt discount				2,009	3,173	6,206
Loss on extinguishment of debt				(607)	(22,553)	(607)
Multi-Currency Line Of Credit [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity				100,000
Line Of Credit Up To $100,000 Due 2013 [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity				50,000
Line of Credit Due Two Thousand Eightteen [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity				280,000
Remaining Borrowing Capacity				$ 252,892
Debt instrument maturity, year				2018
Weighted average interest rate				3.48%
Commitment fee percentage				0.38%
Number Of Pricing Tranches | pricing_tranch				2
Debt Instrument, Issuance Date				Mar. 30, 2011
Long-term Debt				$ 27,108	0
Variable Rate Senior Unsecured Note Due 2018 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 50,000
Debt instrument, maturity date				Mar. 31, 2018
Loss on extinguishment of debt					100
5.75% Senior Unsecured Notes Due 2018
Debt Instrument [Line Items]
Debt instrument maturity, year				2018
Debt Instrument, Face Amount				$ 300,000
Debt instrument, maturity date				May 15, 2018
Debt Instrument, Issuance Date				May 15, 2013
Debt instrument, interest rate				5.75%
Long-term Debt				$ 184,450	196,470
Note Redeem Rate				100.00%
Note Repurchase Rate				101.00%
Repayments of Long-term Debt			$ 12,400		107,200
Loss on extinguishment of debt					6,000
Payments of Debt Extinguishment Costs			400
Write off of Deferred Debt Issuance Cost			200
Original principal amount of repurshased notes			$ 12,000		103,500
Make whole payment premium				$ 18,700
5.25% Convertible Senior Notes Due 2029 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount							$ 115,000
Debt instrument, interest rate				5.25%
Stock Issued During Period, Shares, Conversion of Convertible Securities | shares	747,085
Amortization of debt discount					700	3,300
Contractual interest expenses					1,300	$ 5,900
Repayments of Long-term Debt	$ 44,400	$ 89,500
Loss on extinguishment of debt		1,500
Adjustments to Additional Paid in Capital, Other		30,300
Original principal amount of repurshased notes		$ 58,600
Letter Of Credit Facility [Member]
Debt Instrument [Line Items]
Letter of credit facility, amount				$ 20,000
Standby Letters Of Credit [Member]
Debt Instrument [Line Items]
Line Of Credit Facility, Amount Outstanding				$ 6,000
Waiver And Amendment [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt					106,200
Payments of Debt Extinguishment Costs					14,300
Write off of Deferred Debt Issuance Cost					14,900
Loss on extinguishment of debt					$ 600
Six Point Zero Nine Percentage Senior Unsecured Notes Due Two Thousand Sixteen [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate				6.09%
Seven Point Two Six Percentage Senior Unsecured Notes Due Two Thousand Seventeen [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate				7.26%
Six Point Zero Percentage Senior Unsecured Notes Due Two Thousand Nineteen [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate				6.00%
Six Point Two One Percentage Senior Unsecured Notes Due Two Thousand Twenty One [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate				6.21%
Six Five Eight Senior Unsecured Notes Due Twenty Twenty Two [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate				6.58%
Minimum [Member] | Line of Credit Due Two Thousand Eightteen [Member]
Debt Instrument [Line Items]
Commitment fee percentage				0.25%
Debt instrument maturity days				5 days
Minimum [Member] | LIBOR [Member] | Line of Credit Due Two Thousand Eightteen [Member]
Debt Instrument [Line Items]
Debt instrument basis spread on variable rate				2.00%
Minimum [Member] | Agent Base Rate [Member] | Line of Credit Due Two Thousand Eightteen [Member]
Debt Instrument [Line Items]
Debt instrument basis spread on variable rate				0.50%
Maximum [Member] | Line of Credit Due Two Thousand Eightteen [Member]
Debt Instrument [Line Items]
Commitment fee percentage				0.50%
Debt instrument maturity days				8 days
Maximum [Member] | LIBOR [Member] | Line of Credit Due Two Thousand Eightteen [Member]
Debt Instrument [Line Items]
Debt instrument basis spread on variable rate				3.25%
Maximum [Member] | Agent Base Rate [Member] | Line of Credit Due Two Thousand Eightteen [Member]
Debt Instrument [Line Items]
Debt instrument basis spread on variable rate				1.75%