Shareholder Rights Plan - Additional Information (Detail) - $ / shares	1 Months Ended	9 Months Ended
	Nov. 30, 2008	Dec. 31, 2017
Equity [Abstract]
Dividend distribution ratio of preferred share purchase right for outstanding share of common stock		100.00%
Shareholder rights expiration date	Feb. 10, 2022
Shareholder rights exercise price per share of common stock		$ 118
Shareholder Rights Plan, description of acquired entity		Shareholder Rights Plan provides that if a person or group acquires 15% or more of the Company’s common stock
Shareholder Rights Plan, percentage of acquired entity		15.00%
Shareholder Rights Plan, description of merged entity		Company is thereafter merged into another entity, or if 50% or more of the Company’s consolidated assets or earning power are sold, then the right will entitle its holder to buy common shares of the acquiring entity having a market value equal to two times the then-current exercise price of the right.
Shareholder Rights Plan, percentage of merged entity		50.00%