Calculation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share [Line Items]
Net earnings	$ 11,143	$ 3,829	$ 3,234	$ 81
Amounts allocated to unvested restricted shares	(178)	(54)	(49)	(1)
Net Earnings, Basic, Amounts available to common stockholders	10,965	3,775	3,185	80
Amounts allocated to unvested restricted shares	178	54	49	1
Amounts reallocated to unvested restricted shares	(175)	(53)	(48)	(1)
Net Earnings, Diluted, Amounts available to stockholders and assumed conversions	$ 10,968	$ 3,776	$ 3,186	$ 80
Weighted Average Shares Outstanding, Basic, As reported	32,791,000	32,528,000	32,707,000	32,443,000
Weighted Average Shares Outstanding, Amounts allocated to unvested restricted shares	(523,000)	(455,000)	(492,000)	(375,000)
Weighted Average Shares Outstanding, Amounts available to common stockholders	32,268,000	32,073,000	32,215,000	32,068,000
Weighted Average Shares Outstanding, Amounts allocated to unvested restricted shares	523,000	455,000	492,000	375,000
Weighted Average Shares Outstanding, Non participating share units	244,000	125,000	207,000	92,000
Weighted Average Shares Outstanding, Stock options added under the treasury stock method	264,537	179,640	267,818	230,605
Weighted Average Shares Outstanding, Amounts reallocated to unvested restricted shares	(523,000)	(455,000)	(492,000)	(375,000)
Amounts available to stockholders and assumed conversions	32,777,000	32,378,000	32,690,000	32,391,000
Earnings Per Share, Basic	$ 0.34	$ 0.12	$ 0.10	$ 0.00
Earnings Per Share, Diluted	$ 0.33	$ 0.12	$ 0.10	$ 0.00