Stock Incentive Compensation and Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Share-based Payment Award, Performance Shares, Valuation Assumptions

The following are the weighted average-assumptions used to estimate the fair value for all performance shares issued in each respective year.

	Performance Shares
Year ended December 31,	2016	2015
Expected volatility (1)	14.3% - 14.7%	14.3% - 14.4%
Expected term (in years)	n/a	n/a
Expected dividend yield	n/a	n/a
Risk-free interest rate (1)	0.38% - 1.18%	0.07% - 1.02%

(1) The expected volatility and risk-free interest rate applied are specific to each tranche of performance shares.

Schedule of Share-based Compensation, Options and Premium Option Plan Awards

Premium Option Plan Awards

	Weighted options outstanding		Weighted average exercise price		Weighted average remaining contractual  life	Aggregate intrinsic  value		Range of exercise prices
Balance, December 31, 2013	572,000		$	73.62		$	13,567	$73.06 - $74.24
Options granted	—		—
Options forfeited	—		—
Options expired	—		—
Options exercised	(572,000	)	73.62			13,414
Balance, December 31, 2014	—		$	—		$	—	$	—
Options granted	—		—
Options forfeited	—		—
Options expired	—		—
Options exercised	—		—			—
Balance, December 31, 2015	—		$	—		$	—	$	—
Options granted	—		—
Options forfeited	—		—
Options expired	—		—
Options exercised	—		—			—
Balance, December 31, 2016	—		$	—	0.0	$	—	$	—
Total options exercisable at December 31, 2016	—		$	—	0.0	$	—	$	—

Options

	Weighted options outstanding		Weighted average exercise price		Weighted average remaining contractual  life	Aggregate intrinsic value		Range of exercise prices
Balance, December 31, 2013	828,092		$	48.77	2.9	$	40,221	$37.51 - $59.66
Options granted	—		—					—
Options forfeited	—		—
Options expired	—		—
Options exercised	(60,262	)	49.52			$	2,900
Balance, December 31, 2014	767,830		$	48.71	2.0	$	37,246	$37.51 - $59.66
Options granted	—		—					—
Options forfeited	—		—
Options expired	—		—
Options exercised	(359,618	)	45.09			$	21,205
Balance, December 31, 2015	408,212		$	51.90	1.6	$	25,020	$42.66 - $59.66
Options granted	—		—					—
Options forfeited	—		—
Options expired	—		—
Options exercised	(201,417	)	$	50.59		$	14,806
Balance, December 31, 2016	206,795		$	53.17	0.9	$	17,174	$50.71 - $59.66
Total options exercisable at December 31, 2016	206,795		$	53.17	0.9	$	17,174	$50.71 - $59.66

Schedule of Share-based Compensation, Cash Settled Restricted Stock Units and Performance Shares

Cash Settled Restricted Stock Units

	Number of shares
Nonvested at December 31, 2013	394,145
Awards granted	119,382
Awards vested	(159,094	)
Awards forfeited	(16,110	)
Nonvested at December 31, 2014	338,323
Awards granted	160,817
Awards vested	(144,440	)
Awards forfeited	(28,622	)
Nonvested at December 31, 2015	326,078
Awards granted	135,119
Awards vested	(133,278	)
Awards forfeited	(19,575	)
Nonvested at December 31, 2016	308,344

Performance Shares

	Number of shares (1)		Weighted average  grant-date fair value
Nonvested at December 31, 2013	359,543		$	30.55
Awards granted	102,668		$	46.45
Awards vested	—
Awards forfeited	(213,639	)
Nonvested at December 31, 2014	248,572		$	39.62
Awards granted	103,024		$	44.98
Awards vested	—
Awards forfeited	(121,325	)
Nonvested at December 31, 2015	230,271		$	41.40
Awards granted	77,045		$	48.31
Awards vested	(58,032	)	$	38.80
Awards forfeited	(37,903	)
Nonvested at December 31, 2016	211,381		$	44.63

(1) For performance shares, the number of shares is stated at the maximum number that can be attained if the performance conditions are fully met. Forfeitures represent shares forfeited due to vesting below the maximum attainable as a result of the Company not fully meeting the performance conditions.

Schedule of Share-based Compensation, Restricted Stock Awards

Restricted Stock Awards

	Employee restricted stock awards				Non-employee director restricted stock awards				Total restricted stock awards
	Number of shares		Weighted average grant date fair  value		Number of shares		Weighted average grant date fair  value		Number of shares		Weighted average grant date fair  value
Nonvested at December 31, 2013	569,492		$	76.11	31,486		$	78.57	600,978		$	76.24
Awards granted	215,054		95.79		14,455		95.06		229,509		95.74
Awards vested	(332,725	)	73.74		(15,886	)	74.96		(348,611	)	73.79
Awards forfeited	(99	)	55.80		—		—		(99	)	55.80
Nonvested at December 31, 2014	451,722		$	87.29	30,055		$	88.41	481,777		$	87.36
Awards granted	195,337		102.17		14,575		102.90		209,912		102.22
Awards vested	(168,019	)	82.75		(17,744	)	86.37		(185,763	)	83.10
Awards forfeited	—		—		—		—		—		—
Nonvested at December 31, 2015	479,040		$	94.95	26,886		$	97.61	505,926		$	95.09
Awards granted	179,003		112.41		14,727		114.71		193,730		112.59
Awards vested	(255,873	)	93.98		(16,068	)	96.83		(271,941	)	94.15
Awards forfeited	—		—		—		—		—		—
Nonvested at December 31, 2016	402,170		$	103.34	25,545		$	107.95	427,715		$	103.61