Guarantor Subsidiaries Financial Information - Condensed Cash Flow Statement (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017
Condensed Financial Statements, Captions [Line Items]
Net cash (used for) provided by operating activities	$ 67,904	$ (13,703)
Net cash used for investing activities	(69,100)	(884,629)
Net cash provided by (used for) financing activities	22,764	41,590
Effect of changes in currency exchange rates	(9,395)	42,032
Increase (Decrease) in cash	12,173	(814,710)
Cash, cash equivalents and restricted cash, beginning of period	233,401	1,143,232
Cash and cash equivalents, end of period	245,574	328,522
Elimination
Condensed Financial Statements, Captions [Line Items]
Net cash (used for) provided by operating activities	(47,713)	(13,541)
Net cash used for investing activities	0	0
Net cash provided by (used for) financing activities	47,713	13,541
Effect of changes in currency exchange rates	0	0
Increase (Decrease) in cash	0	0
Cash, cash equivalents and restricted cash, beginning of period	0	0
Cash and cash equivalents, end of period	0	0
Parent
Condensed Financial Statements, Captions [Line Items]
Net cash (used for) provided by operating activities	(116,378)	(50,070)
Net cash used for investing activities	(9,669)	(8,670)
Net cash provided by (used for) financing activities	125,855	58,408
Effect of changes in currency exchange rates	0	0
Increase (Decrease) in cash	(192)	(332)
Cash, cash equivalents and restricted cash, beginning of period	933	2,522
Cash and cash equivalents, end of period	741	2,190
Guarantors
Condensed Financial Statements, Captions [Line Items]
Net cash (used for) provided by operating activities	72,206	65,857
Net cash used for investing activities	(249)	(1,705)
Net cash provided by (used for) financing activities	(72,009)	(62,148)
Effect of changes in currency exchange rates	0	0
Increase (Decrease) in cash	(52)	2,004
Cash, cash equivalents and restricted cash, beginning of period	625	1,226
Cash and cash equivalents, end of period	573	3,230
Non-Guarantors
Condensed Financial Statements, Captions [Line Items]
Net cash (used for) provided by operating activities	159,789	(15,949)
Net cash used for investing activities	(59,182)	(874,254)
Net cash provided by (used for) financing activities	(78,795)	31,789
Effect of changes in currency exchange rates	(9,395)	42,032
Increase (Decrease) in cash	12,417	(816,382)
Cash, cash equivalents and restricted cash, beginning of period	231,843	1,139,484
Cash and cash equivalents, end of period	$ 244,260	$ 323,102

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6676-107765

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3044-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_CashAndCashEquivalentsAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes.

+ References

+ Details

Name:	us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_CondensedFinancialStatementsCaptionsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of increase (decrease) from the effect of exchange rate changes on cash and cash equivalent balances held in foreign currencies.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 230
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=98513438&loc=d3e33268-110906

+ Details

Name:	us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

+ References

+ Details

Name:	us-gaap_NetCashProvidedByUsedInFinancingActivities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.

+ References

+ Details

Name:	us-gaap_NetCashProvidedByUsedInInvestingActivities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 24
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3521-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3536-108585

+ Details

Name:	us-gaap_NetCashProvidedByUsedInOperatingActivities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_ConsolidationItemsAxis=us-gaap_ConsolidationEliminationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConsolidatedEntitiesAxis=us-gaap_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConsolidatedEntitiesAxis=us-gaap_GuarantorSubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConsolidatedEntitiesAxis=us-gaap_NonGuarantorSubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: