Stock-based Compensation - Restricted Stock Awards Activity (Details) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Shares of restricted stock
Outstanding, beginning of period (in shares)	462,910	441,253	503,091
Issued (in shares)	274,012	262,235	175,935
Forfeited (in shares)	(13,390)	(14,895)	(33,352)
Vested (in shares)	(324,700)	(225,683)	(204,421)
Outstanding, end of period (in shares)	398,832	462,910	441,253
Outstanding, Weighted average remaining vesting period	1 year 4 months 24 days	1 year 9 months 18 days
Issued, Weighted average remaining vesting period	3 years 1 month 6 days
Forfeited, Weighted average remaining vesting period	2 years 6 months
Weighted average fair value (per share)
Outstanding at beginning of period, Weighted average fair value (in dollars per share)	$ 43.54	$ 40.82	$ 39.44
Issued, Weighted average fair value (in dollars per share)	51.38	47.03	42.41
Forfeited, Weighted average fair value (in dollars per share)	45.60	43.41	40.64
Vested, Weighted average fair value (in dollars per share)	51.68	42.31	38.71
Outstanding at end of period, Weighted average fair value (in dollars per share)	$ 46.92	$ 43.54	$ 40.82