Stockholders Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			12 Months Ended
	Nov. 30, 2017	May 31, 2017	Jan. 31, 2015	Dec. 31, 2017	Dec. 31, 2015	Dec. 31, 2016
Stockholders Equity Note [Abstract]
Preferred stock, shares authorized				5,000,000		5,000,000
Preferred stock, par value				$ 0.01		$ 0.01
Preferred stock, shares outstanding				0		0
Issuance of common stock, net of offering costs (in shares)	6,440,000	5,000,000	5,447,368
Underwritten public offering amount per share	$ 125.00	$ 71.87	$ 95.00
Issuance of common stock, net of offering costs	$ 784,500	$ 355,200	$ 496,400	$ 1,139,625	$ 496,400
Underwriting discounts and commissions and other offering expenses	$ 20,500	$ 4,200	$ 21,100