Earnings per Share (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Numerator:
Net income from continuing operations	$ 11,153	$ 9,581	$ 24,403	$ 21,605
Net income attributable to non-controlling interests	61	63	140	76
Net income attributable to controlling interest from continuing operations	$ 11,092	$ 9,518	$ 24,263	$ 21,529
Denominator:
Denominator for basic earnings per share (in shares)	22,752	22,691	22,738	22,667
Effect of dilutive securities [Abstract]
Employee stock options and restricted stock units (in shares)	200	242	221	274
Supplemental Executive Retirement Plan (in shares)	117	108	116	106
Denominator for diluted earnings per share (in shares)	23,069	23,041	23,075	23,047
Antidilutive options (in shares)	1,072	1,072	698	698