Stock-BasedCompensation Plans (Tables)

6 Months Ended

Jun. 30, 2018

Summary of Stock Options Issued Pursuant to Stock Incentive Plans

A summary of stock options issued pursuant to the Company’s stock incentive plans is as follows:

	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value  of In-the-Money Options
Outstanding as of December 31, 2017		6,162,717		$	16.83
Granted		170,455			23.36
Exercised		(1,050,518	)		14.19
Forfeited		(52,827	)		19.02
Outstanding as of June 30, 2018		5,229,827		$	17.55		6.40	$	37,215,726
Exercisable as of June 30, 2018		3,688,160		$	16.78		5.69	$	29,089,836

Black-Scholes Option-Pricing Model [Member]

Estimated Fair Value of Options Granted Pricing Model with Weighted-Average Assumptions

The fair value of options that do not vest based on the achievement of certain market conditions granted during the six months ended June 30, 2018 and 2017 were estimated on the date of grant using the Black-Scholes option-pricingmodel, a pricing model acceptable under U.S. GAAP, with the following weighted-average assumptions:

	Six Months Ended June 30, 2018			Six Months Ended June 30, 2017
Expected life (years)		5.6			5.6
Interest rate		2.7	%		1.9	%
Volatility		26.4	%		29.4	%
Dividend yield		—			—

Total Shareholder Return [Member] | Monte Carlo Simulation [Member]

Estimated Fair Value of Options Granted Pricing Model with Weighted-Average Assumptions

The grant date fair value of the TSRs was estimated using the following weighted-average assumptions:

	Six Months Ended June 30, 2018			Six Months Ended June 30, 2017
Expected life (years)		2.9			2.9
Interest rate		2.4	%		1.5	%
Volatility		28.0	%		26.5	%
Dividend Yield		—			—

LTIP Performance Shares [Member]

Summary of Nonvested Performance Share Awards and Changes During Period

A summary of nonvested long-term incentive program performance share awards (“LTIP performance shares”) outstanding as of June 30, 2018, and changes during the period are as follows:

Nonvested LTIP Performance Shares	Number of Shares at Expected Attainment			Weighted- Average Grant Date Fair Value
Nonvested as of December 31, 2017		1,125,035		$	18.94
Forfeited		(44,120	)		19.11
Nonvested as of June 30, 2018		1,080,915		$	18.94

TSR Plan [Member]

Summary of Nonvested Performance Share Awards and Changes During Period

A summary of nonvested TSRs outstanding as of June 30, 2018, and changes during the period are as follows:

Nonvested Total Shareholder Return Awards	Number of Shares at Expected Attainment			Weighted- Average Grant Date Fair Value
Nonvested as of December 31, 2017		143,649		$	24.37
Granted		541,214			31.31
Forfeited		(11,372	)		27.10
Nonvested as of June 30, 2018		673,491		$	29.90

Restricted Share Awards (RSAs) [Member]

Summary of Nonvested Restricted Share and Changes During Period

A summary of nonvested restricted share awards (“RSAs”) as of June 30, 2018, and changes during the period are as follows:

Nonvested Restricted Share Awards	Number of Restricted Share Awards			Weighted-Average Grant Date Fair Value
Nonvested as of December 31, 2017		503,237		$	20.63
Vested		(229,625	)		21.22
Forfeited		(15,945	)		20.12
Nonvested as of June 30, 2018		257,667		$	20.11

Performance-Based Restricted Share Awards [Member]

Summary of Nonvested Performance Share Awards and Changes During Period

A summary of nonvested Performance-Based Restricted Share Awards (“PBRSAs”) as of June 30, 2018, and changes during the period are as follows:

Nonvested Performance-Based Restricted Share Awards	Number of Performance-Based Restricted Share Awards			Weighted-Average Grant Date Fair Value
Nonvested as of December 31, 2017		173,636		$	24.41
Vested		(173,636	)		24.41
Nonvested as of June 30, 2018		—		$	—

Restricted Share Units [Member]

Summary of Nonvested Restricted Share and Changes During Period

A summary of nonvested RSUs as of June 30, 2018, and changes during the period are as follows:

Nonvested Restricted Share Units	Number of Restricted Share Units			Weighted- Average Grant Date Fair Value
Nonvested as of December 31, 2017		—		$	—
Granted		709,168			23.78
Vested		(10,000	)		25.72
Forfeited		(5,992	)		23.36
Nonvested as of June 30, 2018		693,176		$	23.76