Convertible Notes (Details)		3 Months Ended
	Sep. 29, 2014 USD ($)	Mar. 31, 2016 USD ($) item $ / shares	Mar. 31, 2015 USD ($)	Sep. 30, 2014
Interest expense
Total interest expense		$ 3,981,000	$ 3,726,000
Convertible senior notes due October 2021
Notes, issued amount	$ 201,300,000
Capped call transactions payments	$ 20,800,000
Interest rate (as a percent)	3.00%			3.00%
Conversion price per share of convertible notes into common stock | $ / shares		$ 35.13
Convertible notes conversion ratio per 1,000 principal		28.4627
Denominator of the principal amount used in conversion		$ 1,000
Interest expense
Contractual interest expense		1,509,000	1,526,000
Amortization of debt discount		2,315,000	2,026,000
Amortization of debt issuance costs		157,000	174,000
Total interest expense		$ 3,981,000	$ 3,726,000
Convertible senior notes due October 2021 | Conversion of convertible notes into common stock after December 31,2014
Convertible threshold trading days | item		20
Convertible threshold consecutive trading days		30 days
Minimum threshold percentage of stock price trigger		130.00%
Convertible senior notes due October 2021 | Conversion of convertible notes when common share trading price is less than 98% of target ratio
Convertible threshold trading days | item		5
Convertible threshold consecutive trading days		10 days
Denominator of the principal amount for conversion into common stock		$ 1,000
Threshold percentage forcing conversion when less than share price times conversion ratio		98.00%