Employee Retirement Benefit Plans (Details) (401K [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Maximum employee contribution, as a percentage	100.00%
Contributions to the retirement savings plan	$ 0.3	$ 0.1	$ 0.1
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Vesting period	1 year
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Vesting period	5 years