Share Based Compensation, Continued (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Stock Options [Member]
Options outstanding and exercisable [Abstract]
Number of options (in shares)	252,275
Average remaining contractual life (in years)	1 year 7 months 13 days
Weighted average exercise price (in dollars per share)	$ 15.89
Aggregate intrinsic value	$ 4,204
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)	51,975
Average remaining contractual life (in years)	5 months 8 days
Weighted average exercise price (in dollars per share)	$ 3.43
Aggregate intrinsic value	1,514
Stock Options [Member] | $16.89 - $18.80 [Member]
Options outstanding and exercisable [Abstract]
Exercise price range, lower range (in dollars per share)	$ 16.89
Exercise price range, upper range (in dollars per share)	$ 18.80
Number of options (in shares)	113,950
Average remaining contractual life (in years)	1 year 7 months 2 days
Weighted average exercise price (in dollars per share)	$ 17.06
Aggregate intrinsic value	1,766
Stock Options [Member] | $21.46 - $22.67 [Member]
Options outstanding and exercisable [Abstract]
Exercise price range, lower range (in dollars per share)	$ 21.46
Exercise price range, upper range (in dollars per share)	$ 22.67
Number of options (in shares)	86,350
Average remaining contractual life (in years)	2 years 4 months 13 days
Weighted average exercise price (in dollars per share)	$ 21.86
Aggregate intrinsic value	$ 924
Restricted Stock Units (Units) [Member]
Restricted stock units outstanding and exercisable [Abstract]
Number of units (in units)	361,364
Average remaining contractual life (in years)	2 years 9 months 25 days
Weighted average grant fair value (in dollars per share)	$ 31.49
Restricted Stock Units (Units) [Member] | $16.53 - $28.10 [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)	$ 28.10
Number of units (in units)	149,069
Average remaining contractual life (in years)	2 years 7 days
Weighted average grant fair value (in dollars per share)	$ 21.02
Restricted Stock Units (Units) [Member] | $30.99 - $39.43 [Member]
Restricted stock units outstanding and exercisable [Abstract]
Exercise price range, lower range (in dollars per share)	$ 30.99
Exercise price range, upper range (in dollars per share)	$ 39.43
Number of units (in units)	128,075
Average remaining contractual life (in years)	3 years 9 months 14 days
Weighted average grant fair value (in dollars per share)	$ 33.98
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)	79,000
Average remaining contractual life (in years)	2 years 11 months 8 days
Weighted average grant fair value (in dollars per share)	$ 44.66
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 (in years)	2 months 19 days
Weighted average grant fair value (in dollars per share)	$ 70.42