Stock-Based Compensation (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2016 $ / shares shares
Nonvested share units
Number of Shares
Outstanding at beginning of year (in shares) | shares	544
Granted (in shares) | shares	154
Vested (in shares) | shares	(210)
Forfeited (in shares) | shares	(4)
Outstanding at end of period (in shares) | shares	484
Weighted Average Grant Date Fair Value
Outstanding at beginning of year (in dollars per share) | $ / shares	$ 19.84
Granted (in dollars per share) | $ / shares	17.01
Vested (in dollars per share) | $ / shares	18.71
Forfeited (in dollars per share) | $ / shares	17.61
Outstanding at end of period (in dollars per share) | $ / shares	$ 19.45
Time and Performance-Based | Nonvested shares
Number of Shares
Outstanding at beginning of year (in shares) | shares	1,294
Granted (in shares) | shares	209
Outstanding at end of period (in shares) | shares	1,503
Weighted Average Grant Date Fair Value
Outstanding at beginning of year (in dollars per share) | $ / shares	$ 15.15
Granted (in dollars per share) | $ / shares	17.01
Outstanding at end of period (in dollars per share) | $ / shares	$ 15.41
Time-Based | Nonvested shares
Number of Shares
Outstanding at beginning of year (in shares) | shares	890
Granted (in shares) | shares	181
Vested (in shares) | shares	(344)
Forfeited (in shares) | shares	(3)
Outstanding at end of period (in shares) | shares	724
Weighted Average Grant Date Fair Value
Outstanding at beginning of year (in dollars per share) | $ / shares	$ 12.31
Granted (in dollars per share) | $ / shares	17.01
Vested (in dollars per share) | $ / shares	11.66
Forfeited (in dollars per share) | $ / shares	0.27
Outstanding at end of period (in dollars per share) | $ / shares	$ 13.85