Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Share-Based Compensation [Abstract]

Summary of Restricted Stock Unit and Stock Option Activity

	Restricted Stock Units			Stock Options
		Weighted-			Weighted-
		Average			Average
		Grant Date			Exercise/
		Fair Value			(Strike) Price
	Number	Per Share		Number	Per Share
Outstanding as of December 31, 2014	1,056,597	$	26.54	1,989,000	$	19.63
Granted	321,500		23.07	259,000		16.07
Expired or forfeited	(281,560)		23.89	(250,000)		15.97
Vested/exercised	(370,940)		27.07	—		—
Outstanding as of December 31, 2015	725,597	$	25.28	1,998,000	$	19.62
Granted	483,387		19.14	274,000		16.20
Vested/exercised	(52,500)		18.74	(97,500)		12.72
Outstanding as of December 31, 2016	1,156,484	$	22.64	2,174,500	$	19.50
Granted	1,064,000		30.02	539,000		24.54
Expired or cancelled	(20,985)		23.91	(19,466)		26.56
Vested/exercised	(801,515)		19.38	(140,000)		21.41
Outstanding as of December 31, 2017	1,397,984	$	30.11	2,554,034	$	20.45

Summary Of Unrestricted Stock Units Issuance

	Unrestricted Stock Units
		Weighted-Average Grant
Year	Number	Date Fair Value Per Share
2015	68,160	$	21.93
2016	64,603		21.67
2017	99,155		26.26

Weighted-Average Assumptions Used in Estimating Grant Date Fair Values of Stock Option Awards

	Year Ended December 31,
	2017			2016			2015
Total stock options granted		539,000			274,000			259,000
Weighted-average grant date fair value	$	13.11		$	5.31		$	12.48
Weighted-average assumptions:
Risk-free rate		1.81	%		1.2	%		1.3	%
Expected life of options(a)		4.8			4.2			4.7
Expected volatility(b)		43.09	%		40.6	%		45.5	%
Expected quarterly dividends	$	—		$	—		$	—

(a) Calculated using the simplified method due to the terms of the stock options and the limited pool of grantees.

(b) Calculated using historical volatility of the Company’s Common Stock over periods commensurate with the expected life of the option.