Earnings Per Share (Schedule Showing Calculation Of Basic And Diluted Earnings Per Share) (Detail) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Earnings Per Share, Basic And Diluted, By Common Class, Including Two Class Method [Line Items]
Income available to common shareholders	$ 12,560,000		$ 5,186,000		$ 31,953,000		$ 19,833,000
Distributed and undistributed earnings to unvested restricted stock	(240,000)		(91,000)		(613,000)		(379,000)
Distributed and undistributed earnings to common shareholders - Basic	12,320,000	[1]	5,095,000	[1]	31,340,000	[1]	19,454,000	[1]
Undistributed earnings reallocated to unvested restricted stock			4,000		6,000		1,000
Distributed and undistributed earnings to common shareholders - Diluted	12,320,000		5,099,000		31,346,000		19,455,000
Weighted average shares outstanding- Basic	29,463,811	[2]	28,015,846	[2]	29,424,078	[2]	27,405,797	[2]
Weighted average shares outstanding- Diluted	28,950,806		27,677,313		28,939,291		27,124,910
Earnings per common share - Basic	$ 0.43	[1]	$ 0.19	[1]	$ 1.09	[1]	$ 0.72	[1]
Earnings per common share - Diluted	$ 0.43		$ 0.18		$ 1.08		$ 0.72
Distributed earnings	9,838,000		10,083,000		19,679,000		19,076,000
Distributed earnings, per weighted average share	$ 0.34		$ 0.37		$ 0.68		$ 0.71
Undistributed earnings	2,482,000		4,998,000		11,660,000		378,000
Undistributed earnings, per weighted average share	$ 0.09		$ 0.18		$ 0.40		$ 0.01
Weighted average basic shares outstanding, unvested restricted stock	563,882		517,596		549,479		476,896
Unvested Restricted Stock [Member]
Earnings Per Share, Basic And Diluted, By Common Class, Including Two Class Method [Line Items]
Earnings per common share - Basic	$ 0.43	[3]	$ 0.18	[3]	$ 1.12	[3]	$ 0.80	[3]
Earnings per common share - Diluted	$ 0.43		$ 0.17		$ 1.10		$ 0.79
Distributed earnings	192,000		180,000		385,000		372,000
Distributed earnings, per weighted average share	$ 0.34		$ 0.35		$ 0.70		$ 0.78
Undistributed earnings	$ 48,000		$ 89,000		$ 228,000		$ 7,000
Undistributed earnings, per weighted average share	$ 0.09		$ 0.17		$ 0.42		$ 0.02

[1] Total earnings available to common shareholders included distributed earnings of $9,838,000, or $0.34 per weighted average share, and undistributed earnings of $2,482,000, or $0.09 per weighted average share for the three months ended June 30, 2012. Total earnings available to common shareholders included distributed earnings of $10,083,000, or $0.37 per weighted average share, and an undistributed loss of $4,998,000, or $0.18 per weighted average share for the three months ended June 30, 2011. For the six months ended June 30, 2012, total earnings available to common shareholders included distributed earnings of $19,679,000, or $0.68 per weighted average share, and undistributed earnings of $11,660,000, or $0.40 per weighted average share. For the six months ended June 30, 2011, total distributed earnings to common shareholders were $19,076,000, or $0.71 per weighted average share, and undistributed earnings were $378,000, or $0.01 per weighted average share.

[2] Weighted average basic shares outstanding include 563,882 and 517,596 shares of unvested restricted stock for the three months ended June 30, 2012 and 2011, respectively, and 549,479 and 476,896 shares for the six months ended June 30, 2012 and 2011, respectively.

[3] Total earnings available to unvested restricted stock included distributed earnings of $192,000, or $0.34 per weighted average share, and undistributed earnings of $48,000, or $0.09 per weighted average share for the three months ended June 30, 2012. Total earnings available to unvested restricted stock included distributed earnings of $180,000, or $0.35 per weighted average share, and an undistributed loss of $89,000, or $0.17 per weighted average share for the three months ended June 30, 2011. For the six months ended June 30, 2012, total earnings available to unvested restricted stock shares included distributed earnings of $385,000, or $0.70 per weighted average share, and undistributed earnings of $228,000, or $0.42 per weighted average share. For the six months ended June 30, 2011, total distributed earnings were $372,000, or $0.78 per weighted average share, and undistributed earnings were $7,000, or $0.02 per weighted average share.