Shareholders' Equity - Additional Information (Detail) - USD ($)			1 Months Ended		12 Months Ended
	Jun. 10, 2017	May 16, 2017	Jan. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Aug. 13, 2012
Class of Stock [Line Items]
Issuance of common stock Dividend Reinvestment Plan				100,000,000	100,000,000	100,000,000
Number of stock option granted		0			128,000	105,000	286,000
Number of performance-based awards outstanding				53,000		53,000
Number of performance-based awards forfeited					53,000
Share-based compensation expense					$ 1,700,000	$ 2,200,000	$ 1,900,000
Tax benefit related to stock based compensation expense					$ 0	200,000	0
Number of shares authorized in employee stock purchase plan					1,500,000
Employee stock purchase plan period					10 years
Employee stock purchase plan number of shares remain available for future issuance					1,400,000
Discount from market price					15.00%
Employees offering dates intervals					6 months
Employee stock purchase plan expense					$ 83,000	$ 71,000	$ 54,000
Weighted-average fair value of stock options granted					$ 2.68	$ 2.07	$ 4.35
Expected Volatility Rate					39.00%	39.00%	44.00%
Expected Term Period					6 years 3 months 18 days	6 years 6 months	6 years 3 months 18 days
Risk-Free Interest Rate					2.20%	2.10%	1.90%
Expected dividend rate					3.30%	3.60%	2.40%
Cash received from employee stock option exercised					$ 1,100,000	$ 1,300,000	$ 100,000
Intrinsic value of option exercised					$ 2,600,000	$ 1,000,000	$ 200,000
Warrants issued to acquire Icarus Share					250,000
Warrants exercise price					$ 9.07
Warrants expiration date					Dec. 26, 2016
Common stock, shares issued				34,300,209	34,707,924	34,300,209
Warrant outstanding				0	0	0
Aggregate value transaction value of share purchased						$ 1,238,000
Common Stock [Member]
Class of Stock [Line Items]
Common stock, shares issued				89,640		89,640
Shares issued, price per share				$ 9.07		$ 9.07
Share purchased					0	105,000	0
Aggregate value transaction value of share purchased						$ 1,000
Common Stock [Member] | Former Owner of Subsidiary Acquired [Member]
Class of Stock [Line Items]
Share purchased						30,000
Aggregate value transaction value of share purchased						$ 200,000
Common Stock [Member] | Current Segment President [Member]
Class of Stock [Line Items]
Share purchased				75,000		75,000
Aggregate value transaction value of share purchased			$ 1,100,000
Performance Units [Member]
Class of Stock [Line Items]
2017 stock options or stock awards, vesting period	3 years
Maximum shares of common stock participant could receive per performance	77,778
Common stock price threshold consecutive trading days	30 days
Period to earn units based on stock price during thirty consecutive trading days	2 years
Performance Units [Member] | Chief Executive Officer [Member]
Class of Stock [Line Items]
2017 stock options or stock awards, vesting period	3 years
Number of stock awards granted	700,000
Value of stock awards granted	$ 175,000
Restricted Stock and Performance Units [Member]
Class of Stock [Line Items]
Unrecognized compensation expense related to stock options and restricted stock					$ 5,000,000
Weighted average vesting period					2 years 8 months 12 days
Dividend Reinvestment Plan [Member]
Class of Stock [Line Items]
Issuance of common stock Dividend Reinvestment Plan								750,000
2017 Plan [Member]
Class of Stock [Line Items]
Shares available for future grant					2,000,000
Number of stock option granted					128,000
Number of restricted stock awards granted					351,000
2017 Plan [Member] | Common Stock [Member]
Class of Stock [Line Items]
Number of shares reserved for issuance		1,900,000
2017 Plan [Member] | Minimum [Member]
Class of Stock [Line Items]
2017 stock options or stock awards, vesting period					3 years
2017 Plan [Member] | Maximum [Member]
Class of Stock [Line Items]
2017 stock options or stock awards, vesting period					4 years
2017 Plan [Member] | Employee Stock Option [Member]
Class of Stock [Line Items]
2017 stock options or stock awards, vesting period					4 years
2007 Plan [Member]
Class of Stock [Line Items]
Shares available for future grant				414,000		414,000
Number of stock option granted					0	105,000
Number of restricted stock awards granted					54,000	267,000
Number of shares reserved for issuance				3,300,000		3,300,000
2007 Plan [Member] | Minimum [Member]
Class of Stock [Line Items]
2017 stock options or stock awards, vesting period					4 years
2007 Plan [Member] | Maximum [Member]
Class of Stock [Line Items]
2017 stock options or stock awards, vesting period					5 years
2007 Plan [Member] | Employee Stock Option [Member] | Minimum [Member]
Class of Stock [Line Items]
2017 stock options or stock awards, vesting period					3 years
2007 Plan [Member] | Employee Stock Option [Member] | Maximum [Member]
Class of Stock [Line Items]
2017 stock options or stock awards, vesting period					5 years
2007 Plan [Member] | Restricted Stock [Member]
Class of Stock [Line Items]
Number of stock awards granted					405,000
Weighted-average fair value of restricted stock awards granted					$ 9.88	$ 9.76	$ 9.48