Commitments and Contingencies (Details) ft² in Thousands	1 Months Ended			3 Months Ended		6 Months Ended
	Feb. 28, 2015 USD ($) ft² Period	Jul. 31, 2014 USD ($)	May. 31, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jan. 01, 2016 USD ($) ft²	Mar. 31, 2015 USD ($) ft²	Dec. 31, 2014 USD ($)
Rent expense and other operating lease disclosures
Rent expense				$ 1,100,000	$ 700,000	$ 2,100,000	$ 1,300,000
Property and equipment, gross				84,829,000		84,829,000				$ 50,655,000
Capitalized facility leases
Rent expense and other operating lease disclosures
Property and equipment, gross				29,743,000		29,743,000				6,599,000
Lease financing obligation				28,400,000		28,400,000				6,600,000
San Francisco office
Rent expense and other operating lease disclosures
Lease term			10 years
Irrevocable stand-by letter of credit			$ 800,000.0
Lease financing obligation				6,400,000		6,400,000				6,600,000
San Francisco office | Debt redemption period August 2017 to August 2020
Rent expense and other operating lease disclosures
Letter of credit that is subject to annual reduction			200,000.0
San Francisco office | Office lease obligations
Rent expense and other operating lease disclosures
Total minimum lease payments			$ 7,000,000.0
San Francisco office | Capitalized facility leases
Rent expense and other operating lease disclosures
Property and equipment, gross				7,100,000		7,100,000				$ 6,600,000
Lease property, useful life			40 years
Santa Monica office
Rent expense and other operating lease disclosures
Lease term		15 years
Irrevocable stand-by letter of credit		$ 3,500,000.0
Lease financing obligation				22,000,000		22,000,000
Santa Monica office | October, 2019 to October, 2025
Rent expense and other operating lease disclosures
Letter of credit that is subject to annual reduction		1,200,000.0
Santa Monica office | Office lease obligations
Rent expense and other operating lease disclosures
Total minimum lease payments		$ 36,000,000.0
Santa Monica office | Capitalized facility leases
Rent expense and other operating lease disclosures
Property and equipment, gross				$ 22,600,000		$ 22,600,000
Lease property, useful life		40 years
Office lease one, Santa Monica, California
Rent expense and other operating lease disclosures
Irrevocable stand-by letter of credit	$ 500,000.0
Area of office building leased | ft²	17
Optional lease extension term	5 years
Office lease one, Santa Monica, California | Scenario forecast
Rent expense and other operating lease disclosures
Additional area leased | ft²								21
Office lease one, Santa Monica, California | Office lease obligations | Scenario forecast
Rent expense and other operating lease disclosures
Total minimum lease payments								$ 26,000,000
Office lease, Los Angeles
Rent expense and other operating lease disclosures
Lease term	5 years
Area of office building leased | ft²	6
Number of lease extension periods | Period	2
Optional lease extension term	5 years
Office lease, Los Angeles | Office lease obligations
Rent expense and other operating lease disclosures
Total minimum lease payments	$ 3,000,000
Office lease two, Santa Monica, California
Rent expense and other operating lease disclosures
Area of office building leased | ft²	5
Additional area leased | ft²									7
Office lease two, Santa Monica, California | Office lease obligations
Rent expense and other operating lease disclosures
Total minimum lease payments									$ 3,600,000