Stock plans (Tables)

6 Months Ended

Jun. 30, 2011

Stock plans [Abstract]

Options, weighted average assumptions

	Weighted average
	risk free		Weighted average		Expected life
Year	interest rate		dividend yield		(years)		Expected volatility
2008		3.5%		3.2%		7		30.0%
2009		3.9%		3.7%		2		34.6%
2010 (a)		n/a		n/a		n/a		n/a

Options, activity during the period

     Activity with respect to options for the six months ended June 30, 2011 was as follows:

				Weighted Average		Weighted Average
				Grant Date		Grant Date
	Options			Fair Value		Exercise Price
Options outstanding, December 31, 2010		2,723,684		$	6.74	$	20.19
Options granted		—			—		—
Options exercised		(455,033	)		6.96		20.56
Options forfeited		(1,850	)		10.30		20.39
Options outstanding, June 30, 2011		2,266,801		$	6.70	$	20.12
Options exercisable at June 30, 2011		2,178,828		$	6.62	$	20.02

      Activity with respect to options for the six months ended June 30, 2010 was as follows:

				Weighted Average		Weighted Average
				Grant Date		Grant Date
	Options			Fair Value		Exercise Price
Options outstanding, December 31, 2009		3,278,015		$	6.83	$	19.88
Options granted		—			—		—
Options exercised		(51,534	)		5.72		22.34
Options forfeited		(4,317	)		10.30		20.39
Options outstanding, June 30, 2010		3,222,164		$	6.84	$	19.84
Options exercisable at June 30, 2010		2,549,805		$	6.05	$	20.10

     Activity with respect to unvested restricted share units for the six months ended June 30, 2011 was as follows:

				Weighted Average
	Restricted			Grant Date
	Share Units			Fair Value
Restricted share units outstanding, December 31, 2010		47,049		$	25.04
Restricted share units granted		18,388			32.10
Restricted share units vested		(13,340	)		24.72
Restricted share units reinvested		296			25.45
Restricted share units forfeited		—			—
Restricted share units outstanding, June 30, 2011		52,393		$	27.60

     Activity with respect to unvested restricted share units for the six months ended June 30, 2010 was as follows:

				Weighted Average
	Restricted			Grant Date
	Share Units			Fair Value
Restricted share units outstanding, December 31, 2009		78,591		$	24.84
Restricted share units granted		7,952			26.07
Restricted share units vested		(59,019	)		24.76
Restricted share units forfeited		(1,094	)		21.49
Restricted share units outstanding, June 30, 2010		26,430		$	25.51

Other awards, activity during the period

     Activity with respect to unvested restricted share awards for the six months ended June 30, 2011 was as follows:

	Restricted			Weighted Average
	Share			Grant Date
	Awards			Fair Value
Restricted share awards outstanding, December 31, 2010		3,114,039		$	24.33
Restricted share awards granted		590,367			32.16
Restricted share awards vested		(553,615	)		25.46
Restricted share awards forfeited		(13,198	)		27.28
Restricted share awards outstanding, June 30, 2011		3,137,593		$	25.60

      Activity with respect to unvested restricted share awards for the six months ended June 30, 2010 was as follows:

	Restricted			Weighted Average
	Share			Grant Date
	Awards			Fair Value
Restricted share awards outstanding, December 31, 2009		2,525,958		$	23.43
Restricted share awards granted		439,114			26.17
Restricted share awards vested		(323,520	)		23.91
Restricted share awards forfeited		(22,609	)		23.07
Restricted share awards outstanding, June 30, 2010		2,618,943		$	23.83

     Activity with respect to unvested performance share awards for the six months ended June 30, 2011 was as follows:

			Weighted Average
	Performance		Grant Date
	Share Awards		Fair Value
Performance share awards outstanding, December 31, 2010		132,401	$	28.70
Performance share awards granted		146,618		32.64
Performance share awards vested		—		—
Performance share awards forfeited		—		—
Performance share awards outstanding, June 30, 2011		279,019	$	30.77

     Activity with respect to unvested performance share awards for the six months ended June 30, 2010 was as follows:

			Weighted Average
	Performance		Grant Date
	Share Awards		Fair Value
Performance share awards outstanding, December 31, 2009		—	$	—
Performance share awards granted		—		—
Performance share awards vested		—		—
Performance share awards forfeited		—		—
Performance share awards outstanding, June 30, 2010		—	$	—

     Activity with respect to unvested employee seller shares for the six months ended June 30, 2011 was as follows:

				Weighted Average
	Employee			Grant Date
	Seller Shares			Fair Value
Employee seller shares outstanding, December 31, 2010		197,879		$	22.01
Employee seller shares granted		—			—
Employee seller shares vested		—			—
Employee seller shares forfeited		(705	)		22.01
Employee seller shares outstanding, June 30, 2011		197,174		$	22.01

     Activity with respect to unvested employee seller shares for six months ended June 30, 2010 was as follows:

				Weighted Average
	Employee			Grant Date
	Seller Shares			Fair Value
Employee seller shares outstanding, December 31, 2009		410,667		$	22.01
Employee seller shares granted		—			—
Employee seller shares vested		—			—
Employee seller shares forfeited		(3,551	)		22.01
Employee seller shares outstanding, June 30, 2010		407,116		$	22.01

Total share compensation expenses

	Three Months Ended				Six Months Ended
	June 30, 2011		June 30, 2010		June 30, 2011		June 30, 2010
Options	$	179	$	1,036	$	1,426	$	2,074
Restricted share awards		5,792		4,735		14,948		9,061
Restricted share units		97		61		211		234
Performance share awards		528		—		872		—
Employee seller shares		1,032		1,014		2,220		2,053
Total	$	7,628	$	6,846	$	19,677	$	13,422