General - Stock Compensation (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) company $ / shares shares	Sep. 30, 2016 USD ($)
Stock options, Non vested restricted stock awards and nonvested restricted stock units
Stock compensation expense | $	$ 10,300,000	$ 9,200,000	$ 31,800,000	$ 27,600,000
Benefits of tax deductions in excess of recognized stock compensation expense | $			$ 3,700,000	$ 300,000
Minimum
Stock options, Non vested restricted stock awards and nonvested restricted stock units
Estimated forfeitures (as a percent)	0.00%	0.00%	0.00%	0.00%
Maximum
Stock options, Non vested restricted stock awards and nonvested restricted stock units
Estimated forfeitures (as a percent)	4.00%	4.00%	4.00%	4.00%
Stock options
Stock options, Non vested restricted stock awards and nonvested restricted stock units
Grants in period, weighted average grant date fair value (in dollars per share)			$ 17.15
Expected volatility (as a percent)			27.80%
Stock option activity
Outstanding, beginning of period (in shares) | shares			2,843,177
Granted (in shares) | shares			454,596
Forfeited (in shares) | shares			(53,596)
Exercised (in shares) | shares			(583,395)
Outstanding, end of period (in shares) | shares	2,660,782		2,660,782
Vested and expected to vest end of period (in shares) | shares	2,640,924		2,640,924
Exercisable, end of period (in shares) | shares	1,597,984		1,597,984
Weighted average exercise price of stock options
Outstanding, beginning of period (in dollars per share)			$ 57.42
Granted (in dollars per share)			69.44
Forfeited (in dollars per share)			59.65
Exercised (in dollars per share)			52.76
Outstanding, end of period (in dollars per share)	$ 60.46		60.46
Vested and expected to vest end of period (in dollars per share)	60.41		60.41
Exercisable, end of period (in dollars per share)	$ 57.12		$ 57.12
Assumptions used for estimating value of awards granted
Vesting period			3 years
Life of options (Expiration period)			10 years
Restricted stock awards
Nonvested restricted stock awards and units
Outstanding, beginning of period (in shares) | shares			615,472
Awarded (in shares) | shares			14,959
Vested (in shares) | shares			(47,710)
Outstanding, end of period (in shares) | shares	582,721		582,721
Weighted average exercise price of nonvested restricted stock award and units
Outstanding, beginning of period (in dollars per share)			$ 58.71
Awarded (in dollars per share)			70.20
Vested (in dollars per share)			65.24
Outstanding, end of period (in dollars per share)	$ 58.47		$ 58.47
Restricted stock awards | Minimum
Assumptions used for estimating value of awards granted
Vesting period			12 months
Restricted stock awards | Maximum
Assumptions used for estimating value of awards granted
Vesting period			42 months
Restricted Stock Units (RSUs)
Nonvested restricted stock awards and units
Outstanding, beginning of period (in shares) | shares			200,178
Awarded (in shares) | shares			107,417
Vested (in shares) | shares			(117,069)
Forfeited (in shares) | shares			(16,285)
Outstanding, end of period (in shares) | shares	174,241		174,241
Weighted average exercise price of nonvested restricted stock award and units
Outstanding, beginning of period (in dollars per share)			$ 61.65
Awarded (in dollars per share)			68.53
Vested (in dollars per share)			60.52
Forfeited (in dollars per share)			65.48
Outstanding, end of period (in dollars per share)	$ 66.29		$ 66.29
Assumptions used for estimating value of awards granted
Vesting period			3 years
Performance Based Restricted Stock Units (“PSUs”)
Nonvested restricted stock awards and units
Outstanding, beginning of period (in shares) | shares			102,977
Awarded (in shares) | shares			101,989
Forfeited (in shares) | shares			(2,651)
Outstanding, end of period (in shares) | shares	202,315		202,315
Estimated fair value | $			$ 76.24
Weighted average exercise price of nonvested restricted stock award and units
Outstanding, beginning of period (in dollars per share)			$ 93.03
Awarded (in dollars per share)			76.24
Forfeited (in dollars per share)			87.75
Outstanding, end of period (in dollars per share)	$ 84.63		$ 84.63
Assumptions used for estimating value of awards granted
Vesting period			3 years
Expected dividend yield (as a percent)			0.00%
Risk-free interest rate (as a percent)			1.54%
Expected volatility, minimum (as a percent)			18.00%
Expected volatility, maximum (as a percent)			61.00%
Expected volatility, average (as a percent)			33.00%
Number of trading days considered for average share value			30
Number of companies in peer group | company			51
Performance Based Restricted Stock Units (“PSUs”) | Minimum
Assumptions used for estimating value of awards granted
Percentage of shares to be settled			0.00%
Performance Based Restricted Stock Units (“PSUs”) | Maximum
Assumptions used for estimating value of awards granted
Percentage of shares to be settled			200.00%