Common Stock Transactions (Details) $ / shares in Units, $ in Thousands			1 Months Ended			9 Months Ended
	Mar. 17, 2017	Apr. 04, 2016	Jul. 31, 2016 USD ($) $ / shares shares	Apr. 30, 2016 USD ($) item $ / shares shares	Mar. 31, 2016 USD ($) director item $ / shares shares	Sep. 30, 2016 USD ($)
Proceeds from issuance of Common Stock						$ 613,913
Common Stock
Number of shares issued | shares			5,347,500
Price per share of common stock | $ / shares			$ 81.00
Proceeds from issuance of Common Stock			$ 408,900
Gross proceeds from issuance of common stock			$ 433,100
Common Stock | Private placement
Number of shares issued | shares					4,404,658
Price per share of common stock | $ / shares					$ 35.19
Number of directors | director					3
Proceeds from issuance of private placement					$ 155,000
Number of days for calculating weighted average price per share	10 days
Number of placement agents used | item					0
Common Stock | Stock Purchase Agreement With JJDC
Number of shares issued | shares				1,130,198
Price per share of common stock | $ / shares				$ 44.24
Proceeds from issuance of Common Stock				$ 50,000
Number of days for calculating weighted average price per share		5 days
Number of placement agents used | item				0
Common Stock | Underwriters' option
Number of shares issued | shares			697,500