Stockholders' Equity - Compensation Plans and Stock Options (Details) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
	May 18, 2016 multiplier shares	Dec. 31, 2017 USD ($) $ / shares shares	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	May 21, 2014 shares
Share-based compensation
Vesting period										3 years
Assumptions used for estimating value of awards granted
Tax benefit from exercise of stock options and vesting of stock awards												$ 4,073
Net change to additional paid-in capital related to tax benefits (deficiencies)												3,530
Tax benefit from exercise of stock options and vesting of stock awards		$ 4,123	$ (11,739)	$ (5,661)	$ (11,806)	$ (26,469)	$ (18,631)	$ (12,615)	$ (12,013)	$ (25,083)	$ (69,728)	$ (42,409)
Stock options
Share-based compensation
Vesting period										3 years
Life of options (Expiration period)										10 years
Stock option activity
Outstanding, beginning of period (in shares) | shares					2,843,177				2,939,840	2,843,177	2,939,840	3,321,063
Granted (in shares) | shares										525,596	501,960	1,004,321
Forfeited (in shares) | shares										(79,350)	(104,680)	(244,658)
Exercised (in shares) | shares										(831,186)	(493,943)	(1,140,886)
Outstanding, end of period (in shares) | shares		2,458,237				2,843,177				2,458,237	2,843,177	2,939,840
Vested and expected to vest end of period (in shares) | shares		2,441,446								2,441,446
Exercisable, end of period (in shares) | shares		1,403,228								1,403,228
Weighted average exercise price of stock options
Outstanding, beginning of period (in dollars per share) | $ / shares					$ 57.42				$ 55.13	$ 57.42	$ 55.13	$ 50.58
Granted (in dollars per share) | $ / shares										71.35	64.10	62.65
Forfeited (in dollars per share) | $ / shares										61.39	57.23	60.25
Exercised (in dollars per share) | $ / shares										53.79	50.60	47.41
Outstanding, end of period (in dollars per share) | $ / shares		$ 61.50				$ 57.42				61.50	$ 57.42	$ 55.13
Vested and expected to vest end of period (in dollars per share) | $ / shares		61.45								61.45
Exercisable, end of period (in dollars per share) | $ / shares		$ 57.22								$ 57.22
Weighted average remaining contractual term
Outstanding										7 years 15 days
Vested and expected to vest										7 years 15 days
Exercisable										5 years 11 months 1 day
Aggregate intrinsic value
Outstanding		$ 86,158								$ 86,158
Vested and expected to vest end of period		85,706								85,706
Exercisable, end of period		$ 55,195								$ 55,195
Closing stock price (in dollars per share) | $ / shares		$ 96.55								$ 96.55
Total pre-tax intrinsic value of options exercised										$ 23,800	$ 9,300	$ 21,800
Grants in period, weighted average grant date fair value (in dollars per share) | $ / shares										$ 17.64	$ 15.05	$ 13.69
Assumptions used for estimating value of awards granted
Risk-free interest rate (as a percent)										1.79%	1.16%	1.28%
Expected life										4 years	4 years	4 years
Expected volatility (as a percent)										27.75%	27.75%	25.03%
Expected dividend yield (as a percent)										0.00%	0.00%	0.00%
Unrecognized compensation expense		$ 10,000								$ 10,000
Unrecognized compensation expense, period of recognition										1 year 8 months 5 days
Aggregate fair value of options vested		8,800								$ 8,800
Tax benefit from exercise of stock options and vesting of stock awards												$ 4,100
Net change to additional paid-in capital related to tax benefits (deficiencies)												3,500
Deficiency of tax deductions in recognized stock compensation expenses										100	$ 200	$ 600
Tax benefit from exercise of stock options and vesting of stock awards										5,600	800
Excess tax benefits of tax deductions in recognized stock compensation expenses										$ 5,700	$ 1,000
Restricted Stock Units (RSUs)
Share-based compensation
Vesting period										3 years
Assumptions used for estimating value of awards granted
Unrecognized compensation expense		6,000								$ 6,000
Unrecognized compensation expense, period of recognition										1 year 9 months 18 days
Performance Based Restricted Stock Units (“PSUs”)
Share-based compensation
Vesting period										3 years
Assumptions used for estimating value of awards granted
Risk-free interest rate (as a percent)										1.54%	1.00%	1.00%
Expected dividend yield (as a percent)										0.00%	0.00%	0.00%
Unrecognized compensation expense		$ 7,700								$ 7,700
Unrecognized compensation expense, period of recognition										1 year 5 months 1 day
2016 Management Incentive Plan
Share-based compensation
Maximum number of shares available | shares	4,000,000
Multiplier for delivery of shares under full-value awards | multiplier	1.60
Number of shares available for grant | shares		3,724,939								3,724,939
2014 Employee Stock Purchase Plan
Share-based compensation
Maximum number of shares available | shares													200,000
Number of shares available for grant | shares		72,187								72,187
Number of shares of common stock issued under purchase plans | shares										56,426	48,815