Property and Equipment, net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Property and Equipment, net
Property and equipment, gross	$ 84,829		$ 84,829		$ 50,655
Less: Accumulated depreciation	(24,467)		(24,467)		(19,924)
Total property and equipment, net	60,362		60,362		30,731
Property and equipment capitalized but not placed in service	24,400		24,400		8,100
Total depreciation and amortization expense	4,119	$ 2,972	8,044	$ 6,086
Property and Equipment
Property and Equipment, net
Total depreciation and amortization expense	3,100	1,900	6,000	3,900
Computer equipment, software, and internally developed software
Property and Equipment, net
Property and equipment, gross	46,315		46,315		37,110
Furniture and fixtures
Property and Equipment, net
Property and equipment, gross	2,764		2,764		2,335
Leasehold Improvements
Property and Equipment, net
Property and equipment, gross	6,007		6,007		4,611
Capitalized facility leases
Property and Equipment, net
Property and equipment, gross	29,743		29,743		6,599
Interest costs related to premises	500		1,200
Lease financing obligation	28,400		28,400		6,600
Internally developed software
Property and Equipment, net
Amortization	2,200	$ 1,200	4,100	$ 2,300
Santa Monica capitalized facility lease
Property and Equipment, net
Property and equipment capitalized but not placed in service	$ 22,600		$ 22,600
San Francisco capitalized facility lease
Property and Equipment, net
Property and equipment capitalized but not placed in service					$ 6,600