Stock Options and Other Equity-Based Incentive Instruments - Information about Options (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Information about Options
Intrinsic value of options exercised	$ 1,777,000	$ 138,000	$ 2,087,000
Fair value of options that vested	1,150,000	1,083,000	830,000
Total compensation costs for options recognized in income	1,150,000	1,083,000	830,000
Total tax benefit recognized in income related to compensation costs for options	$ 484,000	$ 455,000	$ 349,000
Weighted average fair value of grants (per option)	$ 8.91	$ 6.63	$ 6.27