General - Stock Compensation (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) company $ / shares shares	Jun. 30, 2016 USD ($)
Stock options, Non vested restricted stock awards and nonvested restricted stock units
Stock compensation expense | $	$ 11,400,000	$ 9,500,000	$ 21,500,000	$ 18,400,000
Benefits of tax deductions in excess of recognized stock compensation expense | $			$ 1,000,000	$ 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)			$ 17.10
Expected volatility (as a percent)			27.80%
Stock option activity
Outstanding, beginning of period (in shares) | shares			2,843,177
Granted (in shares) | shares			425,596
Forfeited (in shares) | shares			(42,789)
Exercised (in shares) | shares			(123,563)
Outstanding, end of period (in shares) | shares	3,102,421		3,102,421
Vested and expected to vest end of period (in shares) | shares	3,078,102		3,078,102
Exercisable, end of period (in shares) | shares	2,001,180		2,001,180
Weighted average exercise price of stock options
Outstanding, beginning of period (in dollars per share)			$ 57.42
Granted (in dollars per share)			69.21
Forfeited (in dollars per share)			58.31
Exercised (in dollars per share)			50.86
Outstanding, end of period (in dollars per share)	$ 59.29		59.29
Vested and expected to vest end of period (in dollars per share)	59.24		59.24
Exercisable, end of period (in dollars per share)	$ 56.13		$ 56.13
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			(17,675)
Outstanding, end of period (in shares) | shares	612,756		612,756
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)			64.01
Outstanding, end of period (in dollars per share)	$ 58.83		$ 58.83
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			(10,068)
Outstanding, end of period (in shares) | shares	180,458		180,458
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)			65.19
Outstanding, end of period (in dollars per share)	$ 66.28		$ 66.28
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			(550)
Outstanding, end of period (in shares) | shares	204,416		204,416
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)			76.24
Outstanding, end of period (in dollars per share)	$ 84.70		$ 84.70
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%