Common Stock and Other Equity Related Transactions - At-market offering (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	May 04, 2015
Class of Stock [Line Items]
Par or stated value per share (usd per share)	$ 0.01	$ 0.01
Shares of Common Stock sold (in shares)	683,548	0	0
Commissions paid to sales agents	$ 1,122	$ 491	$ 595
Private Placement
Class of Stock [Line Items]
Aggregate offering price				$ 125,000
Total gross proceeds	50
Common stock, available for issuance	$ 75,000
Private Placement | Common Stock
Class of Stock [Line Items]
Shares of Common Stock sold (in shares)	683,548
Weighted average price (in usd per share)	$ 73.15
Commissions paid to sales agents	$ 1