Shareholders' Equity - Summary of Stock Options Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options, Options outstanding, Beginning balance	485,000
Number of Options, Granted or assumed	0	0	0
Number of Options, Conversion to common stock	(216,000)
Number of Options, Options outstanding and exercisable, Ending balance	269,000
Weighted Average Exercise Price, Options outstanding, Beginning balance	$ 23.77
Weighted Average Exercise Price, Conversion to common stock	23.40
Weighted Average Exercise Price, Options outstanding and exercisable, Ending balance	$ 24.06
Weighted Average Remaining Life (Years), Options outstanding		2 years 4 months 24 days
Weighted Average Remaining Life (Years), Options outstanding and exercisable	2 years 2 months 19 days
Aggregated Intrinsic Value, Options outstanding and exercisable	$ 14,727