Cash Equivalents and Investments (Narrative) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	$ 0	$ 435,000
Gains (losses) on sales of available-for-sale securities	$ 882,000	$ 997,000