Stock Option and Compensation Plans - Summary of Stock Option Activity (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common Stock Options
Outstanding at beginning of year (in shares)	3,009	3,680	2,708
Granted (in shares)	972	764	1,744
Exercised (in shares)	(428)	(1,133)	(621)
Expired or forfeited (in shares)	(194)	(302)	(151)
Outstanding at end of year (in shares)	3,359	3,009	3,680
Weighted Average Exercise Price
Outstanding at beginning of year (in dollars per share)	$ 30.43	$ 21.03	$ 9.41
Granted (in dollars per share)	60.40	47.31	33.92
Exercised (in dollars per share)	15.73	10.31	4.75
Expired or forfeited (in dollars per share)	48.63	34.09	28.50
Outstanding at end of year (in dollars per share)	$ 39.92	$ 30.43	$ 21.03
Options exercisable at end of year (in shares)	1,531	955	993
Weighted average grant date fair value (per share) of options granted during the period (in dollars per share)	$ 38.18	$ 31.33	$ 24.41