Benefit Plans (Narrative) (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Benefit Plans [Line Items]
Percentage of defined plan agreement	30.00%
Contributions to plan	$ 1.1	$ 1.0	$ 1.0
Supplemental Retirement Plans expenses	0.4	0.5	0.7
Employee Share Purchase Plan [Member]
Benefit Plans [Line Items]
Common stock purchase at a discount	15.00%
Number of common shares purchased	30,000	29,000	44,000
Shares purchase consideration	0.5	0.4	0.4
Expenses recorded to the share purchase plan	$ 0.1	$ 0.1	$ 0.3