Stock-Based Compensation - Restricted Stock Activity (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2017 $ / shares shares
Shares (in 000's)
Non-vested at beginning of period (in shares) | shares	153
Granted (in shares) | shares	98
Vested (in shares) | shares	(26)
Forfeited (in shares) | shares	(1)
Non-vested at end of period (in shares) | shares	224
Weighted-Average Grant Date Fair Value
Non-vested at beginning of period (in dollars per share) | $ / shares	$ 57.43
Granted (in dollars per share) | $ / shares	63.39
Vested (in dollars per share) | $ / shares	56.94
Forfeited (in dollars per share) | $ / shares	58.95
Non-vested at end of period (in dollars per share) | $ / shares	$ 60.09