Fair Value Measurements (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Cash and cash equivalents		$ 1,602	$ 233	$ 516	$ 988
Cash Convertible Notes Hedges [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		12,632
Purchases of Level 3 instruments		0
Settlements of Level 3 instruments		0
Gains (Losses) included in Earnings		35,729
Balance at end of period		48,361
Fifth Amended Credit Facility [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Debt Instrument, Fair Value		73,500
Debt Instrument, Carrying Amount		73,500
Cash Convertible Notes [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Debt Instrument, Fair Value		187,700
Debt Instrument, Carrying Amount		137,900
Aggregate principal of convertible notes		150,000
Cash Conversion Derivative [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		(12,632)
Purchases of Level 3 instruments		0
Settlements of Level 3 instruments		0
Gains (Losses) included in Earnings		(35,729)
Balance at end of period		(48,361)
Gallup Derivative [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		(6,339)
Purchases of Level 3 instruments		0
Settlements of Level 3 instruments		6,339
Gains (Losses) included in Earnings		0
Balance at end of period		0
Recurring [Member] | Foreign Currency Exchange Contracts [Member]
Assets [Abstract]
Assets, netting	[1]		(26)
Assets, net fair value			258
Liabilities [Abstract]
Liabilities, netting	[1]		(26)
Liabilities, net fair value			22
Recurring [Member] | Foreign Currency Exchange Contracts [Member] | Level 2 [Member]
Assets [Abstract]
Assets, gross fair value			284
Liabilities [Abstract]
Liabilities, gross fair value			48
Recurring [Member] | Foreign Currency Exchange Contracts [Member] | Level 3 [Member]
Assets [Abstract]
Assets, gross fair value			0
Liabilities [Abstract]
Liabilities, gross fair value			0
Recurring [Member] | Foreign Currency Exchange Contracts [Member] | Gross Fair Value [Member]
Assets [Abstract]
Assets, gross fair value			284
Liabilities [Abstract]
Liabilities, gross fair value			48
Recurring [Member] | Interest Rate Swaps [Member]
Liabilities [Abstract]
Liabilities, netting	[1]		0
Liabilities, net fair value			397
Recurring [Member] | Interest Rate Swaps [Member] | Level 2 [Member]
Liabilities [Abstract]
Liabilities, gross fair value			397
Recurring [Member] | Interest Rate Swaps [Member] | Level 3 [Member]
Liabilities [Abstract]
Liabilities, gross fair value			0
Recurring [Member] | Interest Rate Swaps [Member] | Gross Fair Value [Member]
Liabilities [Abstract]
Liabilities, gross fair value			397
Recurring [Member] | Cash Convertible Notes Hedges [Member]
Assets [Abstract]
Assets, netting	[1]	0	0
Assets, net fair value		48,361	12,632
Recurring [Member] | Cash Convertible Notes Hedges [Member] | Level 2 [Member]
Assets [Abstract]
Assets, gross fair value			0
Recurring [Member] | Cash Convertible Notes Hedges [Member] | Level 3 [Member]
Assets [Abstract]
Assets, gross fair value		48,361	12,632
Recurring [Member] | Cash Convertible Notes Hedges [Member] | Gross Fair Value [Member]
Assets [Abstract]
Assets, gross fair value		48,361	12,632
Recurring [Member] | Cash Conversion Derivative [Member]
Liabilities [Abstract]
Liabilities, netting	[1]	0	0
Liabilities, net fair value		48,361	12,632
Recurring [Member] | Cash Conversion Derivative [Member] | Level 2 [Member]
Liabilities [Abstract]
Liabilities, gross fair value			0
Recurring [Member] | Cash Conversion Derivative [Member] | Level 3 [Member]
Liabilities [Abstract]
Liabilities, gross fair value		48,361	12,632
Recurring [Member] | Cash Conversion Derivative [Member] | Gross Fair Value [Member]
Liabilities [Abstract]
Liabilities, gross fair value		$ 48,361	12,632
Recurring [Member] | Gallup Derivative [Member]
Liabilities [Abstract]
Liabilities, netting	[1]		0
Liabilities, net fair value			6,339
Recurring [Member] | Gallup Derivative [Member] | Level 2 [Member]
Liabilities [Abstract]
Liabilities, gross fair value			0
Recurring [Member] | Gallup Derivative [Member] | Level 3 [Member]
Liabilities [Abstract]
Liabilities, gross fair value			6,339
Recurring [Member] | Gallup Derivative [Member] | Gross Fair Value [Member]
Liabilities [Abstract]
Liabilities, gross fair value			$ 6,339

[1] This column reflects the impact of netting derivative assets and liabilities by counterparty when a legally enforceable master netting agreement exists.