Notes Payable - 2.25% Convertible Senior Notes due 2022 - General Information (Details) - USD ($)	1 Months Ended	3 Months Ended
	Jun. 30, 2015	Mar. 31, 2017
Notes Payable
Net proceed received		$ 146,250,000
2.25% Convertible Senior Notes due in 2022 | Convertible Senior Notes
Notes Payable
Aggregate principal amount of notes issued	$ 335,700,000
Net proceed received	324,000,000
Fees and expenses	11,700,000
Payments for convertible bond hedges	$ 21,100,000
Annual interest rate of notes (as a percent)	2.25%
Principal amount used for debt instrument conversion ratio	$ 1,000
Maximum period of the sole remedy for event failures in the Indenture		180 days
Amortization period	7 years
Class A common stock | 2.25% Convertible Senior Notes due in 2022 | Convertible Senior Notes
Notes Payable
Initial conversion rate, number of shares to be issued per $1000 of principal amount (in shares)	60.3209
Principal amount used for debt instrument conversion ratio	$ 1,000
Initial conversion price (in dollars per share)	$ 16.58
Shares issuable upon conversion of debt (in shares)	20,249,665
Number of trading days	30 days
Minimum percentage of stock price	130.00%
Number of business days immediately after any five consecutive trading day period during the measurement period	5 days
Number of consecutive trading days before five business days during the measurement period	5 days
Repurchase price, as percentage of principal amount, if company undergoes change of control	100.00%
Class A common stock | Maximum | 2.25% Convertible Senior Notes due in 2022 | Convertible Senior Notes
Notes Payable
Number of trading days	20 days
Percentage of the trading price to the product of the sale price of the entity's common stock and the conversion rate	98.00%
Class A common stock | Minimum | 2.25% Convertible Senior Notes due in 2022 | Convertible Senior Notes
Notes Payable
Percentage of aggregate principal amount payable, in case of event of default	25.00%