Weighted Average Assumptions used in Black Scholes Option Valuation Model (Detail)		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Expected annual volatility	[1]	40.00%	45.00%	47.00%
Expected term in years	[2]	4 years 4 months 24 days	4 years 6 months	4 years 4 months 24 days
Risk-free interest rate	[3]	1.21%	1.34%	1.33%
Expected annual dividend yield	[4]	0.63%	0.68%	0.44%

[1] The expected annual volatility for each grant is determined based on the average of historical daily price changes of the Company's common stock over a period of time which approximates the expected option term.

[2] The expected option term for each grant is determined based on the historical exercise behavior of employees and post-vesting employment termination behavior.

[3] The risk-free interest rate is based on the yield of U.S. Treasury securities with a maturity that is commensurate with the expected option term at the time of grant.

[4] The expected annual dividend yield is based on the weighted-average of the dividend yield assumptions used for options granted during the applicable period. The expected annual dividend has historically been based on the expected dividend of $0.06 per share, per year ($0.015 per share, per quarter times 4 quarters), on a post-split basis, divided by the average stock price. On May 27, 2014, the Company announced an increase in its quarterly cash dividend from $0.015 to $0.03 per share. Thus, for grants made after this date, the expected annual dividend is based on the expected dividend of $0.12 per share, per year ($0.03 per share, per quarter times 4 quarters), divided by the average stock price.