Shareholders' Equity - Rollforward of RSUs, PSUs amd Restricted Shares (Details) - Restricted Shares/Units shares in Thousands	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Restricted Shares/Units
Nonvested at beginning of period (in shares) | shares	13,516
Granted (in shares) | shares	3,924
Vested (in shares) | shares	(4,142)
Forfeited (in shares) | shares	(350)
Nonvested at end of period (in shares) | shares	12,948
Expected to vest at end of period (in shares) | shares	11,946
Wtd. Avg. Grant Date Fair Value
Nonvested at beginning of period (in usd per share) | $ / shares	$ 29.39
Granted (in usd per share) | $ / shares	42.88
Vested (in usd per share) | $ / shares	27.75
Forfeited (in usd per share) | $ / shares	33.29
Nonvested at end of period (in usd per share) | $ / shares	33.90
Expected to vest at end of period (in usd per share) | $ / shares	$ 33.90