Fair Value Measurements of Assets and Liabilities - Convertible Debt (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013
Fixed rate convertible debt on balance sheet
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debt	$ 89,010
Fair value of fixed rate convertible debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible debt	$ 195,749

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. Fair value of convertible debt at the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Convertible Security

-URI http://asc.fasb.org/extlink&oid=6509036

Name:	us-gaap_ConvertibleDebtFairValueDisclosures
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant