Share Based Compensation, Continued (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Stock Options [Member]
Options outstanding and exercisable [Abstract]
Number of options (in shares)	259,150
Average remaining contractual life	1 year 10 months 13 days
Weighted average exercise price (in dollars per share)	$ 15.80
Aggregate intrinsic value	$ 2,847
Stock Options [Member] | $2.98 - $4.58 [Member]
Options outstanding and exercisable [Abstract]
Exercise price range, lower range (in dollars per share)	$ 2.98
Exercise price range, upper range (in dollars per share)	$ 4.58
Number of options (in shares)	55,350
Average remaining contractual life	8 months 12 days
Weighted average exercise price (in dollars per share)	$ 3.42
Aggregate intrinsic value	1,293
Stock Options [Member] | $16.90 - $18.80 [Member]
Options outstanding and exercisable [Abstract]
Exercise price range, lower range (in dollars per share)	$ 16.9
Exercise price range, upper range (in dollars per share)	$ 18.8
Number of options (in shares)	114,450
Average remaining contractual life	1 year 10 months 2 days
Weighted average exercise price (in dollars per share)	$ 17.06
Aggregate intrinsic value	1,113
Stock Options [Member] | $21.50 - $22.67 [Member]
Options outstanding and exercisable [Abstract]
Exercise price range, lower range (in dollars per share)	$ 21.5
Exercise price range, upper range (in dollars per share)	$ 22.67
Number of options (in shares)	89,350
Average remaining contractual life	2 years 8 months
Weighted average exercise price (in dollars per share)	$ 21.85
Aggregate intrinsic value	$ 441
Restricted Stock Units (Units) [Member]
Restricted stock units outstanding and exercisable [Abstract]
Number of units (in units)	362,727
Average remaining contractual life	2 years 5 months 1 day
Weighted average grant fair value (in dollars per share)	$ 31.84
Restricted Stock Units (Units) [Member] | $16.53 - $31.69 [Member]
Restricted stock units outstanding and exercisable [Abstract]
Exercise price range, lower range (in dollars per share)	$ 16.53
Exercise price range, upper range (in dollars per share)	$ 31.69
Number of units (in units)	301,607
Average remaining contractual life	2 years 7 months 24 days
Weighted average grant fair value (in dollars per share)	$ 29.30
Restricted Stock Units (Units) [Member] | $35.67 - $39.43 [Member]
Restricted stock units outstanding and exercisable [Abstract]
Exercise price range, lower range (in dollars per share)	$ 35.67
Exercise price range, upper range (in dollars per share)	$ 39.43
Number of units (in units)	32,400
Average remaining contractual life	2 years 5 months 8 days
Weighted average grant fair value (in dollars per share)	$ 38.60
Restricted Stock Units (Units) [Member] | $40.73 - $45.70 [Member]
Restricted stock units outstanding and exercisable [Abstract]
Exercise price range, lower range (in dollars per share)	$ 40.73
Exercise price range, upper range (in dollars per share)	$ 45.70
Number of units (in units)	19,600
Average remaining contractual life	1 year 5 months 1 day
Weighted average grant fair value (in dollars per share)	$ 44.59
Restricted Stock Units (Units) [Member] | $52.47 - $62.07 [Member]
Restricted stock units outstanding and exercisable [Abstract]
Exercise price range, lower range (in dollars per share)	$ 52.47
Exercise price range, upper range (in dollars per share)	$ 62.07
Number of units (in units)	3,900
Average remaining contractual life	2 months 19 days
Weighted average grant fair value (in dollars per share)	$ 56.52
Restricted Stock Units (Units) [Member] | $66.35 - $81.18 [Member]
Restricted stock units outstanding and exercisable [Abstract]
Exercise price range, lower range (in dollars per share)	$ 66.35
Exercise price range, upper range (in dollars per share)	$ 81.18
Number of units (in units)	5,220
Average remaining contractual life	5 months 23 days
Weighted average grant fair value (in dollars per share)	$ 70.42