Shareholders' Equity - Additional Information (Detail) - Common Stock [Member] - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	May 31, 2019
Issuance of common stock	336	336
Common stock price per share	$ 60.61	$ 60.61
Cash proceeds from sale of common stock	$ 20,349,000
Sale of common stock, sales agent commissions	483,000
Stock issuance cost	251,000
Net cash proceeds from sale of common stock	$ 19,615,000
Maximum [Member]
Aggregate offering price of common stock			$ 30,000,000