Supplemental Cash Flow Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Cash Flow Information [Abstract]
Converted instrument amount	$ 3.9	$ 1.0
Interest payments	2.9	2.9	$ 2.9
Cash paid for taxes	$ 0.0	$ 0.0	$ 0.0