Convertible Senior Notes Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		12 Months Ended
	May. 31, 2013	Mar. 31, 2016		Dec. 31, 2015		Dec. 31, 2014	[1]
Schedule of Convertible Senior Notes
Stock repurchased and retired during period, shares	600,000	1,138,461	[1],[2]	4,907,675	[1],[3]	1,961,085
Stock repurchased and retired during period, value	$ 30,000,000	$ 47,461,000	[1],[2]	$ 215,911,000	[1],[3]	$ 88,815,000
Strike price of warrants	$ 83.18
Proceeds from issuance of warrants	$ 43,600,000
Designated as Hedging Instrument | Debt
Schedule of Convertible Senior Notes
Note hedge, aggregate amount	$ 63,500,000
Convertible Senior Notes | Convertible Senior Notes 0.25% Due May 15, 2018
Schedule of Convertible Senior Notes
Contractual interest rate		0.25%
Maturity date		May 15, 2018
Conversion rate		15.5847
Denomination amount		$ 1,000
Convertible senior notes, face amount		$ 300,000,000		$ 300,000,000
Conversion price		$ 64.17
Number of days out of thirty that common stock price exceeded conversion price		20
Number of consecutive trading days in period		30 days
Holders of notes conversion percentage of conversion price		130.00%
Notes trading price percentage		98.00%
Debt issuance cost		$ 6,400,000
Deferred tax assets		600,000
Debt issuance costs attributable to the equity component		$ 1,700,000

[1] All shares were purchased pursuant to the publicly announced share repurchase program described in footnote (2) below. Shares are reported in a period based on the settlement date of the applicable repurchase.

[2] repurchases for the three months ended March 31, 2016.

[3] The Company entered into an accelerated share repurchase ("ASR") in the second quarter of 2015 under which a prepayment of $75 million was made. Final settlement of the ASR occurred on August 3, 2015, resulting in the delivery to the Company of 0.8 million shares of the Company’s common stock and a return of cash for the remaining amount not settled in shares of $38.2 million. In total, approximately 0.8 million shares of common stock were repurchased under the ASR for $36.8 million, resulting in an average price paid per share of $46.49 under the ASR.