Initial Public Offering Initial Public Offering (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Aug. 14, 2013
Initial Public Offering [Line Items]
Public offering transaction-related costs	$ 508	$ 10,008	$ 0
IPO [Member]
Initial Public Offering [Line Items]
Public offering transaction-related costs		10,008		2,200
IPO [Member] | Termination of management services agreement [Member]
Initial Public Offering [Line Items]
Public offering transaction-related costs		9,000
IPO [Member] | Other Public Offering Transaction Related Costs [Member]
Initial Public Offering [Line Items]
Public offering transaction-related costs		$ 1,008