Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2016

Stock-based Compensation [Abstract]

Compensation Cost and Related Tax Benefits

	Three Months Ended June 30,				Six Months Ended June 30,
(in millions)	2016		2015		2016		2015
Stock-based compensation expense	$	2.7	$	4.2	$	5.5	$	7.5
Tax benefit		(0.9)		(1.4)		(1.9)		(2.6)
Stock-based compensation expense, net of taxes	$	1.8	$	2.8	$	3.6	$	4.9

Summary of Stock Option Plan Activity

	Six Months Ended June 30,
	2016			2015
(in whole shares and dollars)	Shares		Weighted Average Exercise Price	Shares		Weighted Average Exercise Price
Outstanding, beginning of period	1,619,948	$	56.57	2,236,620	$	46.61
Granted	524,940		82.74	659,850		70.28
Exercised	(495,242)		48.57	(204,444)		44.29
Forfeited or cancelled	(161,207)		66.80	(90,137)		51.52
Outstanding, end of period	1,488,439		67.36	2,601,889		52.63

Summary of Restricted Stock Activity

	Six Months Ended June 30,
	2016			2015
(in whole shares and dollars)	Shares		Weighted Average Grant Date Fair Value	Shares		Weighted Average Grant Date Fair Value
Time-based restricted stock units:
Outstanding, beginning of period	301,897	$	54.54	384,923	$	45.63
Granted	141,949		83.47	92,409		70.61
Vested	(135,863)		42.44	(95,787)		41.56
Forfeited	(18,831)		67.15	(20,988)		48.90
Outstanding, end of period	289,152		73.61	360,557		52.93
Performance-based and market-based restricted stock units:
Outstanding, beginning of period	196,142	$	47.89	218,338	$	44.24
Granted	118,736		73.14	82,025		48.55
Vested	(144,141)		41.11	(77,854)		38.82
Forfeited	(56,500)		63.52	(14,451)		44.68
Outstanding, end of period	114,237		74.97	208,058		47.93