Share-Based Compensation Plans - Summary of Restricted Stock Activity (Details) - Restricted stock awards - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Non- Vested Shares
Non-Vested Shares, Outstanding, Beginning Balance	229,990
Non-Vested Shares, Granted	158,360	89,500	101,510
Non-Vested Shares, Vested	(71,100)
Non-Vested Shares, Forfeited	(17,130)
Non-Vested Shares, Outstanding, Ending Balance	300,120	229,990
Weighted Average Fair Value
Weighted Average Fair Value, Outstanding, Beginning Balance (in dollars per share)	$ 74.90
Weighted Average Fair Value, Granted (in dollars per share)	75.46	$ 95	$ 71
Weighted Average Fair Value, Vested (in dollars per share)	53.56
Weighted Average Fair Value, Forfeited (in dollars per share)	80.92
Weighted Average Fair Value, Outstanding, Ending Balance (in dollars per share)	$ 79.90	$ 74.90
Aggregate Fair Value
Aggregate Fair Value, Outstanding, Beginning Balance	$ 17,225,411
Aggregate Fair Value, Granted	11,949,751
Aggregate Fair Value, Vested	(3,808,262)	$ (1,500,000)	$ (4,300,000)
Aggregate Fair Value, Forfeited	(1,386,273)
Aggregate Fair Value, Outstanding, Ending Balance	$ 23,980,627	$ 17,225,411