Segment Information - Revenue by Geographical Location (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 440,900	$ 380,585	$ 314,027
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	394,234	334,412	287,716
Foreign Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 46,666	$ 46,173	$ 26,311