Stock-based compensation plans (Tables)

12 Months Ended

Dec. 31, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Restricted Stock and Restricted Stock Unit Activity

A summary of restricted stock and restricted stock unit activity follows:

	Restricted Stock Units Outstanding			Weighted- Average Grant Price		Restricted Stock Outstanding			Weighted- Average Grant Price
Unvested at January 1, 2015		789,411		$	99.53		761,645		$	96.36
Granted		324,772			114.14		218,183			113.33
Assumed in acquisition		215,215			119.85		—			—
Vested		(357,457	)		98.35		(325,518	)		92.68
Cancelled		(3,443	)		100.95		(28,422	)		104.60
Unvested at December 31, 2015		968,498		$	109.38		625,888		$	103.82

Summary of Stock Option Activity

A summary of stock option activity follows:

	Stock Options Outstanding			Weighted-Average				Aggregate Intrinsic Value (In thousands)
				Exercise Price		Life (In Years)
Outstanding at January 1, 2015		3,432,870		$	105.31
Granted		200			113.16
Assumed in acquisition		1,843,159			156.82
Exercised		(954,684	)		107.06
Expired		(97,835	)		137.50
Outstanding at December 31, 2015		4,223,710		$	126.65		1.7	$	43,761
Exercisable at December 31, 2015		4,223,266		$	126.65		1.7	$	43,755