Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2015

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Company's Option Activity

A summary of the Company’s option activity and related information for the three years ended December 31, 2015 is as follows:

	Number of options			Weighted- average price		Weighted- average remaining contractual term (in years)		Aggregate intrinsic value (in millions)
Balance at December 31, 2012		2,838,553		$	24.37
Options granted		192,800			29.14
Options exercised	(1,237,341)				24.71
Options cancelled/forfeited/expired		(21,950	)		25.20
Balance at December 31, 2013		1,772,062			24.68
Options granted		203,600			32.79
Options exercised	(612,682)				21.55
Options cancelled/forfeited/expired		(19,220	)		30.35
Balance at December 31, 2014		1,343,760			27.25
Options granted		456,200			31.69
Options exercised		(270,650	)		19.81
Options cancelled/forfeited/expired		(118,660	)		29.58
Balance at December 31, 2015		1,410,650		$	29.91		3.82	$	(6.6	)
Exercisable at December 31, 2015		662,345		$	27.53		1.89	$	(1.5	)
Expected to vest after December 31, 2015		673,475		$	31.64		5.53	$	(4.3	)

Options Outstanding and Options Exercisable by Exercise Price with Weighted-Average Remaining Contractual Life for Options Outstanding and Weighted-Average Exercise Price

The following table indicates the options outstanding and options exercisable by exercise price with the weighted-average remaining contractual life for the options outstanding and the weighted-average exercise price at December 31, 2015:

	Options Outstanding						Options Exercisable
Exercise price	Number outstanding at December31, 2015		Weighted- average remaining contractual life (Years)		Weighted- average grant date value		Number exercisable at December 31, 2015		Weighted- average grant date value
$15 – 20		2,400		0.17	$	15.62		2,400	$	15.62
20 – 25		153,855		1.22		23.86		151,965		23.86
25 – 30		508,795		2.04		28.98		424,960		29.01
30 – 35		736,200		5.59		32.04		79,480		32.62
35 – 40		9,400		4.96		37.83		3,540		37.90
$15 – 40		1,410,650		3.82	$	29.91		662,345	$	27.53

Schedule of Weighted-Average Assumptions Used to Determine Fair Value of Option Granted

The fair value of each option granted was estimated on the date of grant using the Black-Scholes option-pricing model using the following weighted-average assumptions:

	Year Ended December 31,
	2015			2014			2013
Expected term (in years)		5.0			5.0			5.0
Expected volatility		31.1	%		40.5	%		50.3	%
Expected dividend yields		3.2	%		3.0	%		3.3	%
Risk-free interest rates		1.6	%		1.5	%		0.8	%

Summary of Company's Restricted Stock Units Activity

The following table summarizes the activity of the Company’s RSUs, which includes service-based and performance-based awards, for the three years ended December 31, 2015:

				Weighted-		Aggregate
				average		intrinsic
	Number			grant Date		value
	of shares			fair value		(in millions)
Balance at December 31, 2012		262,820			28.22
RSUs granted		150,300			26.89
RSUs vested		(87,840	)		24.98
RSUs cancelled/forfeited/expired		(4,300	)		29.24
Balance at December 31, 2013		320,980			28.47
RSUs granted		118,864			30.85
RSUs vested		(120,721	)		27.30
RSUs cancelled/forfeited/expired		(7,540	)		30.34
Balance at December 31, 2014		311,583			29.78
RSUs granted		79,300			31.86
RSUs vested		(89,915	)		27.97
RSUs cancelled/forfeited/expired		(80,320	)		31.35
Balance at December 31, 2015		220,648		$	30.70	$	5.6