Stock Compensation Plans - Restricted Share Activity (Details) - Restricted Stock [Member]	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding - beginning of year, Number of Shares | shares	687,030
Outstanding - beginning of year, Weighted-average Grant Date Fair Value | $ / shares	$ 39.61
Granted, Number of shares | shares	485,975
Granted, Weighted-average Grant Date Fair Value | $ / shares	$ 41.39
Vested, Number of shares | shares	(103,953)
Vested, Weighted-average Grant Date Fair Value | $ / shares	$ 36.37
Canceled or expired, Number of Shares | shares	(54,282)
Canceled or expired, Weighted-average Grant Date Fair Value | $ / shares	$ 41.44
Outstanding - end of year, Number of Shares | shares	1,014,770
Outstanding - end of year, Weighted-average Grant Date Fair Value | $ / shares	$ 40.69