Commitments and Contingencies - Santa Monica Office Lease (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jul. 31, 2014	Dec. 31, 2016	Dec. 31, 2017
Operating Leased Assets [Line Items]
Property and equipment net, capitalized		$ 66,941	$ 70,710
Lease Financing Obligation Current and Noncurrent Amount		30,900	31,400
Lease
Operating Leased Assets [Line Items]
Expected cumulative base rent over initial lease term			77,096
Santa Monica Office
Operating Leased Assets [Line Items]
Total future minimum lease commitments period	15 years
Standby letter of credit	$ 3,500
Lease Financing Obligation Current and Noncurrent Amount		$ 24,000	24,500
Estimated useful life		40 years
Santa Monica Office | Capitalized facility leases
Operating Leased Assets [Line Items]
Property and equipment net, capitalized		$ 30,600	$ 30,600
Santa Monica Office | Debt Redemption Period October 1, 2019 to October 1, 2025
Operating Leased Assets [Line Items]
Amount of annual reduction of letter of credit	1,200
Santa Monica Office | Lease
Operating Leased Assets [Line Items]
Expected cumulative base rent over initial lease term	$ 36,000