Capital Stock and Equity Awards - Summary of Option Activity (Details) - Options - $ / shares	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Shares
Beginning of period (in shares)	1,479,236	2,234,699
Granted (in shares)	0	205,244
Exercised (in shares)	(255,609)	(443,114)
Forfeited (in shares)	(29,446)	(50,062)
End of period (in shares)	1,194,181	1,946,767
Exercisable, end of period (in shares)	876,816	992,395
Weighted- Average Exercise Price
Beginning of period (in dollars per share)	$ 27.81	$ 22.84
Granted (in dollars per share)	0.00	42.24
Exercised (in dollars per share)	21.14	18.72
Forfeited (in dollars per share)	36.26	27.97
End of period (in dollars per share)	29.04	25.69
Exercisable, end of period (in dollars per share)	$ 26.59	$ 20.95
Vesting period (in years)	7 years
Minimum
Weighted- Average Exercise Price
Vesting period (in years)	2 years
Maximum
Weighted- Average Exercise Price
Vesting period (in years)	4 years