Stockholders' Equity (Details) - USD ($)		1 Months Ended		12 Months Ended
	Sep. 26, 2014	Aug. 31, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jan. 31, 2016	Feb. 28, 2014
Class of Warrant or Right [Line Items]
Exercise price after adjustment (USD per share)									$ 34.12
Number of shares sold in an underwritten public offering (shares)		3,600,000	4,600,000
Issue share price (USD per share)		$ 63.75	$ 44.00
Proceeds from the issuance of common stock, net of underwriting discounts and other expenses		$ 218,600,000	$ 188,800,000	$ 0	$ 407,477,000	$ 0
Common stock, shares authorized (shares)				117,500,000	117,500,000	58,750,000
Share repurchase program, authorized amount (shares)								$ 60,000,000.0
Common stock repurchased and retired (shares)				831,744
Stock repurchased and retired during period, value				$ 20,000,000
Average share price (USD per share)				$ 24.05
Rights
Class of Warrant or Right [Line Items]
Exercise price after adjustment (USD per share)	$ 80.00						$ 250.00
Beneficial ownership to acquire to make the rights exercisable (percent)	4.99%						20.00%