Income Taxes - Components of the Provision for Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current:
U.S. Federal	$ 1,855	$ 958	$ 26
U.S. State	1	(5)	0
Ireland	0	0	0
Total current provision	1,856	953	26
Deferred:
U.S. Federal	(1,045)	(538)	(20)
U.S. State	0	0	0
Ireland	0	0	0
Total deferred benefit	(1,045)	(538)	(20)
Provision for income taxes	$ 811	$ 415	$ 6