Stock-Based Compensation Plans (Details 4) - Performance awards - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Performance awards
Outstanding at the beginning of the period (in shares)	239,902	189,765	0
Granted (in shares)	85,636	136,276	191,008
Forfeited (in shares)	(6,143)	(23,140)	(1,243)
Increase (decrease) in awards based on performance (in shares)	14,697	(46,790)
Converted to restricted stock (in shares)	(95,826)	(16,209)
Outstanding at the ending of the period (in shares)	238,266	239,902	189,765
Weighted average grant date fair value per award
Outstanding at the beginning of the period (in dollars per share)	$ 95.20	$ 70.00	$ 0.00
Granted (in dollars per share)	148.49	117.43	70.00
Forfeited (in dollars per share)	110.34	76.22	70.00
Change in awards based on performance (in dollars per share)	78.50	74.37
Converted to restricted stock (in dollars per share)	78.50	74.37
Outstanding at the ending of the period (in dollars per share)	$ 119.65	$ 95.20	$ 70.00
Grants in period based on shareholder metrics (in shares)	55,162	60,391
Grants in period based on financial metrics (in shares)	30,474	75,885