Shareholders' capital (Tables)

12 Months Ended

Dec. 31, 2016

Equity [Abstract]

Number of Common Shares

Number of common shares: 

	2016	2015
Common shares, beginning of year	255,869,419	238,149,468
Public offering (i) and subscription receipts (ii)	12,938,457	14,355,000
Dividend reinvestment plan (iii)	2,322,618	3,230,697
Exercise of share-based awards (c)	2,956,524	134,254
Common shares, end of year	274,087,018	255,869,419

Schedule of Shares Issued and Outstanding

The Company has the following Series A and Series D preferred shares issued and outstanding as at December 31, 2016 and 2015:

Preferred shares	Number of shares	Price per share		Carrying amount
Series A	4,800,000	$	25	$	116,546
Series D	4,000,000	$	25	97,259
				$	213,805

Share-Based Compensation Expense

For the year ended December 31, 2016, APUC recorded $5,675 (2015 - $5,330) in total share-based compensation expense detailed as follows: 

	2016		2015
Share options	$	3,006	$	2,742
Directors deferred share units	683		404
Employee share purchase	238		158
Performance share units	1,748		2,026
Total share-based compensation	$	5,675	$	5,330

Fair Value of Share Options Granted

The following assumptions were used in determining the fair value of share options granted: 

	2016			2015
Risk-free interest rate	0.9		%	1.3		%
Expected volatility	23		%	38		%
Expected dividend yield	4.5		%	4.0		%
Expected life	5.50 years			8 years
Weighted average grant date fair value per option	$	1.26		$	2.45

Stock Option Activity

Share option activity during the years is as follows: 

	Number of awards		Weighted average exercise price		Weighted average remaining contractual term (years)	Aggregate intrinsic value
Balance at January 1, 2015	5,537,127		$	6.09	4.96	$	19,648
Granted	1,627,525		9.75		8.00
Balance at December 31, 2015	7,164,652		$	6.92	4.74	$	28,561
Granted	2,596,025		10.85		8.00
Exercised	(3,715,663	)	5.25		2.06	20,790
Balance at December 31, 2016	6,045,014		$	9.64	6.27	$	10,595
Exercisable at December 31, 2016	2,120,539		$	8.36	5.16	$	6,420

Performance Stock Units

A summary of the PSUs follows: 

	Number of awards		Weighted average grant-date fair value		Weighted average remaining contractual term (years)	Aggregate intrinsic value
Balance at January 1, 2015	440,086		$	6.57	1.81	$	4,242
Granted, including dividends	212,250		9.72		2.62	—
Exercised	(41,131	)	6.86		—	381
Forfeited	(47,089	)	8.30		—	—
Balance at December 31, 2015	564,116		$	7.59	1.63	$	6,155
Granted, including dividends	219,315		11.62		2.00	—
Exercised	(181,875	)	8.29		—	2,115
Forfeited	(22,568	)	9.64		—	—
Balance at December 31, 2016	578,988		$	9.82	1.74	$	6,595
Exercisable at December 31, 2016	215,790		$	8.22	—	$	2,458