Stockholders' Equity (Details) $ / shares in Units, $ in Thousands			1 Months Ended	4 Months Ended	12 Months Ended
	May 06, 2016 USD ($) sales_agent	Aug. 28, 2015 USD ($) sales_agent	Jul. 31, 2016 USD ($) $ / shares shares	May 06, 2016 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) item $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($)
Changes In Equity And Comprehensive Income Line Items [Line Items]
Common stock, shares authorized (in shares)					500,000,000	500,000,000
Common stock, par value (in dollars per share) | $ / shares					$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)					50,000,000	50,000,000
Preferred stock, par value (in dollars per share) | $ / shares					$ 0.01	$ 0.01
Common stock, shares issued (in shares)					127,103,750	126,007,091
Common stock, shares outstanding (in shares)					127,103,750	126,007,091
Preferred stock, shares issued (in shares)					0	0
Preferred stock, shares outstanding (in shares)					0	0
Number of votes, common stockholder rights | item					1
Net proceeds from sale of stock | $					$ 90,231	$ 0	$ 123,424
“At the market” equity program
Changes In Equity And Comprehensive Income Line Items [Line Items]
Aggregate offering price | $	$ 400,000	$ 400,000
Number of sales agents | sales_agent	5	5
Common stock sold (in shares)			550,000	831,300	933,789
Average sales price (in dollars per share) | $ / shares			$ 92.04	$ 89.66
Net proceeds from sale of stock | $			$ 50,062	$ 73,360
Available for issuance | $					$ 257,929