Employee Benefits (Details 1) - Restricted Shares Subject Only to a Service Condition	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Restricted shares subject only to a service condition:
Non-vested, January 1, 2015 (in shares) | shares	440,073
Granted (in shares) | shares	198,295
Vested (in shares) | shares	(162,287)
Forfeited (in shares) | shares	(79,483)
Non-vested, December 31, 2015 (in shares) | shares	396,598
Non-vested, January 1, 2015 (in dollars per share) | $ / shares	$ 56.40
Granted (in dollars per share) | $ / shares	38.64
Vested (in dollars per share) | $ / shares	57.14
Forfeited (in dollars per share) | $ / shares	50.92
Non-vested, December 31, 2015 (in dollars per share) | $ / shares	$ 48.31