Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands			6 Months Ended
	Jul. 28, 2015	Jan. 28, 2015	Jun. 30, 2016	Jun. 30, 2015
Common stock - public offering
Aggregate proceeds received, net of underwriting discounts and commissions and offering costs			$ 0	$ 158,414
Common Stock
Common stock - public offering
Shares sold (in shares)	4,054,054	4,000,000
Share issue price (in dollars per share)	$ 74.00	$ 36.75
Aggregate proceeds received, net of underwriting discounts and commissions and offering costs	$ 281,500	$ 137,800
Common Stock | Underwriters Over-Allotment Option
Common stock - public offering
Shares sold (in shares)	608,108	600,000
Common Stock | Total of Public Offering and exercise of Underwriters Over-Allotment Option
Common stock - public offering
Aggregate proceeds received, net of underwriting discounts and commissions and offering costs	$ 323,800	$ 158,400