Share-Based Payments - Stock Options (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Summary of activity for stock options
Beginning balance (in shares)	2,114	4,456	18,082
Exercised (in shares)	(2,114)	(2,342)	(13,626)
Ending balance (in shares)	0	2,114	4,456
Summary of activity for stock options, weighted average exercise price
Beginning balance (USD per share)	$ 25.02	$ 24.64	$ 23.00
Exercised (USD per share)	25.02	24.13	22.47
Ending balance (USD per share)	$ 0.00	$ 25.02	$ 24.64