Stock-Based Compensation - Schedule of Deferred Stock Units Activity (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Deferred Stock Units
Units (in thousands)
Outstanding at January 1, 2016 (in shares) | shares	164
Granted (in shares) | shares	44
Vested and distributed (in shares) | shares	(31)
Outstanding at December 31, 2016 (in shares) | shares	177
Weighted Average Grant Date Fair Value
Outstanding at January 1, 2016 (in dollars per share) | $ / shares	$ 44.90
Granted (in dollars per share) | $ / shares	47.50
Vested and distributed (in dollars per share) | $ / shares	54.97
Outstanding at December 31, 2016 (in dollars per share) | $ / shares	$ 43.77
Restricted Stock Units (RSUs)
Units (in thousands)
Outstanding at January 1, 2016 (in shares) | shares	5,710
Granted (in shares) | shares	3,609
Vested and distributed (in shares) | shares	(2,910)
Forfeited (in shares) | shares	(566)
Outstanding at December 31, 2016 (in shares) | shares	5,843
Weighted Average Grant Date Fair Value
Outstanding at January 1, 2016 (in dollars per share) | $ / shares	$ 59.51
Granted (in dollars per share) | $ / shares	59.60
Vested and distributed (in dollars per share) | $ / shares	59.59
Forfeited (in dollars per share) | $ / shares	46.65
Outstanding at December 31, 2016 (in dollars per share) | $ / shares	$ 59.94