Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2018

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, 2018 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, 2015		1,410,650		$	29.91
Options granted		881,800			25.26
Options exercised		(368,085	)		27.34
Options cancelled/forfeited/expired		(339,930	)		28.62
Balance at December 31, 2016		1,584,435			28.14
Options granted		299,600			34.66
Options exercised		(398,275	)		28.94
Options cancelled/forfeited/expired		(276,900	)		28.04
Balance at December 31, 2017		1,208,860			28.14
Options granted		—			—
Options exercised		(332,810	)		29.49
Options cancelled/forfeited/expired		(30,450	)		28.27
Balance at December 31, 2018		845,600		$	29.57		4.18	$	18.6
Exercisable at December 31, 2018		303,225		$	29.71		3.78	$	6.6
Expected to vest after December 31, 2018		517,884		$	29.50		4.41	$	11.4

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, 2018:

	Options Outstanding						Options Exercisable
Exercise price	Number outstanding at December31, 2018		Weighted- average remaining contractual life (Years)		Weighted- average grant date value		Number exercisable at December 31, 2018		Weighted- average grant date value
$20 – 25		349,990		4.17	$	24.60		109,150	$	24.60
$25 – 30		33,970		2.19	$	27.99		24,460	$	29.10
$30 – 35		448,300		4.32	$	33.31		165,675	$	33.03
$35 – 40		7,900		4.58	$	38.83		3,600	$	38.56
$40 – 45		5,440		5.67	$	40.37		340	$	40.37
$20 – 45		845,600		4.18	$	29.57		303,225	$	29.71

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,
	2018		2017			2016
Expected term (in years)		—		5.0			5.0
Expected volatility		—		26.1	%		28.7	%
Expected dividend yields		—		3.0	%		4.1	%
Risk-free interest rates		—		2.0	%		1.2	%

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, 2018:

				Weighted-		Aggregate
				average		intrinsic
	Number			grant date		value
	of shares			fair value		(in millions)
Balance at December 31, 2015		220,648		$	30.70
RSUs granted		31,900			25.75
RSUs vested		(59,008	)		29.69
RSUs cancelled/forfeited/expired		(68,300	)		29.33
Balance at December 31, 2016		125,240			30.66
RSUs granted		70,960			34.53
RSUs vested		(36,336	)		26.99
RSUs cancelled/forfeited/expired		(66,200	)		32.63
Balance at December 31, 2017		93,664			33.62
RSUs granted		97,260			49.47
RSUs vested		(30,214	)		33.16
RSUs cancelled/forfeited/expired		(21,200	)		33.88
Balance at December 31, 2018		139,510		$	44.73	$	7.2