Debt - Convertible Subordinated Notes (Details) (Zero-coupon convertible subordinated notes [Member])	12 Months Ended
	Dec. 31, 2013
Zero-coupon convertible subordinated notes [Member]
Debt Instrument [Line Items]
Contingent cash interest accrual rate	0.125%
Number of days used to establish average market price of zero coupon subordinated notes	5