Shareholders' Equity (Stock Option Activity) (Details)	3 Months Ended
	Mar. 31, 2017 $ / shares shares
Shares Underlying Stock Options
Outstanding beginning balance, Shares underlying stock options and restricted stock awards (in shares) | shares	2,627,462
Granted, Shares underlying stock options and restricted stock awards (in shares) | shares	1,308,625
Exercised, Shares underlying stock options and restricted stock awards (in shares) | shares	(130,555)
Forfeited, Shares underlying stock options and restricted stock awards (in shares) | shares	(16,867)
Outstanding ending balance, Shares underlying stock options and restricted stock awards (in shares) | shares	3,788,665
Weighted- Average Exercise Price per Share
Outstanding beginning balance, Weighted - average exercise price (usd per share) | $ / shares	$ 21.07
Granted, Weighted - average exercise price (usd per share) | $ / shares	19.52
Exercised, Weighted - average exercise price (usd per share) | $ / shares	15.89
Forfeited, Weighted - average exercise price (usd per share) | $ / shares	19.20
Outstanding ending balance, Weighted - average exercise price (usd per share) | $ / shares	$ 20.72