STOCKHOLDERS' EQUITY (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Changes in stockholders' equity
Balances at the beginning of the period (in shares)			33,567,730
Balances at the beginning of the period			$ 353,176,000
Net income	14,543,000	9,292,000	22,269,000	15,131,000
Issuance of common shares in connection with equity incentive plans			539,000
Repurchase and retirement of common stock			(1,524,000)
Stock-based compensation			4,704,000
Tax benefit from vesting of restricted shares			889,000
Balances at the end of the period (in shares)	33,794,868		33,794,868
Balances at the end of the period	380,053,000		380,053,000
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			336,000
Issuance of common shares in connection with equity incentive plans (in shares)			310,066
Issuance of common shares in connection with equity incentive plans			2,000
Repurchase and retirement of common stock (in shares)			(82,928)
Balances at the end of the period (in shares)	33,794,868		33,794,868
Balances at the end of the period	338,000		338,000
Additional Paid-In Capital
Changes in stockholders' equity
Balances at the beginning of the period			236,823,000
Issuance of common shares in connection with equity incentive plans			537,000
Repurchase and retirement of common stock			(1,524,000)
Stock-based compensation			4,704,000
Tax benefit from vesting of restricted shares			889,000
Balances at the end of the period	241,429,000		241,429,000
Retained Earnings
Changes in stockholders' equity
Balances at the beginning of the period			116,017,000
Net income			22,269,000
Balances at the end of the period	$ 138,286,000		$ 138,286,000