STOCKHOLDERS' EQUITY (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Changes in stockholders' equity
Balances at the beginning of the period (in shares)	33,567,730
Balances at the beginning of the period	$ 353,176
Net income	7,726	5,839
Issuance of common shares in connection with equity incentive plans	119
Repurchase and retirement of common stock	(292)
Stock-based compensation	2,160
Tax benefit from vesting of restricted shares	161
Balances at the end of the period (in shares)	33,613,832
Balances at the end of the period	363,050
Common Stock
Changes in stockholders' equity
Balances at the beginning of the period (in shares)	33,567,730
Balances at the beginning of the period	336
Issuance of common shares in connection with equity incentive plans	62,151
Repurchase and retirement of common stock (in shares)	(16,049)
Balances at the end of the period (in shares)	33,613,832
Balances at the end of the period	336
Additional Paid-In Capital
Changes in stockholders' equity
Balances at the beginning of the period	236,823
Issuance of common shares in connection with equity incentive plans	119
Repurchase and retirement of common stock	(292)
Stock-based compensation	2,160
Tax benefit from vesting of restricted shares	161
Balances at the end of the period	238,971
Retained Earnings
Changes in stockholders' equity
Balances at the beginning of the period	116,017
Net income	7,726
Balances at the end of the period	$ 123,743